Interconnectable ultrasound transducer probes and related methods and apparatus

ABSTRACT

Ultrasound devices and methods are described, including a repeatable ultrasound transducer probe having ultrasonic transducers and corresponding circuitry. The repeatable ultrasound transducer probe may be used individually or coupled with other instances of the repeatable ultrasound transducer probe to create a desired ultrasound device. The ultrasound devices may optionally be connected to various types of external devices to provide additional processing and image rendering functionality.

RELATED APPLICATIONS

This application is a continuation of and claims the benefit under 35U.S.C. §120 of U.S. patent application Ser. No. 14/337,813, filed onJul. 22, 2014 and entitled “INTERCONNECTABLE ULTRASOUND TRANSDUCERPROBES AND RELATED METHODS AND APPARATUS” which claims the benefit under35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No.61/857,682, filed on Jul. 23, 2013 and entitled “INTERCONNECTABLEULTRASOUND TRANSDUCER PROBES AND RELATED METHODS AND APPARATUS”, both ofwhich are incorporated herein by reference in their entireties.

BACKGROUND

1. Field

The technology described herein relates to ultrasound devices andrelated methods and apparatus.

2. Related Art

Ultrasound imaging probes exist. Conventionally, distinct probes arerequired for imaging in two dimensions (2D) or three dimensions (3D).Separate design and manufacture of such distinct probes are required,which increases cost and limits versatility of the probes.

Also, conventional ultrasound probes are designed for connection tospecialized control systems. The probes themselves include transducersbut typically lack any control circuitry for controlling operation ofthe transducers or processing signals received by the transducers.Rather, control of the transducers and processing of signals received bythe transducers is performed by the specialized control systems. Thespecialized control systems are available to only a select few. Suchdesign further limits the versatility and accessibility of theultrasound probes.

SUMMARY

Aspects of the present application provide a highly integrated,microfabricated ultrasound transducer probe which may serve as astand-alone ultrasound transducer probe and which is configured to beinterconnectable with other such transducer probes to form ultrasounddevices capable of two-dimensional (2D) and three-dimensional (3D)ultrasound imaging. In some embodiments, the ultrasound transducer probeincludes microfabricated ultrasonic transducers integrated withintegrated circuitry controlling operation of the ultrasonic transducersand providing multiple electronic interfaces for connecting theultrasound transducer probe to one or more external devices. In someembodiments, the device is a complete ultrasound-on-a-chip containingall transducers and electronics to perform collection and processing ofultrasound signals. Final image processing may be performed on or offthe chip.

The external devices may perform some processing and/or image generationwith ultrasound data provided by the ultrasound transducer probe. Insome embodiments, the ultrasonic transducers of the ultrasoundtransducer probe may be configured suitably to enable 2D imaging and thetransducer probe itself may include a substrate with a suitable geometryto provide a 1D aperture or 1.5D aperture in some embodiments. A 1.5Daperture, and thus a 1.5D device (e.g., a 1.5D ultrasound transducerprobe) is one in which focusing is provided along one dimension of theaperture. The integrated circuitry may be at least partiallyprogrammable to allow for coordinated operation between multiple suchinterconnected ultrasound transducer probes, for example when providinghigher dimensional imaging functionality than that provided by a singleinstance of the ultrasound transducer probe.

The ultrasound transducer probes may be operated as sensors and/orsources of ultrasound energy. For example, the ultrasound transducerprobes may be operated as ultrasound imaging probes in some embodiments,sensing ultrasound energy from a subject. The ultrasound energy may beemitted by the same ultrasound transducer probe detecting the ultrasoundenergy, or may be emitted by a distinct source. In some embodiments, theultrasound transducer probe may be operated as a source, for example asource of high intensity focused ultrasound (HIFU).

Further aspects of the present application provide ultrasound devicesmaking use of the microfabricated ultrasound transducer probe describedabove, ultrasound imaging techniques utilized by such devices, andmethods of fabricating, operating, and/or interconnecting themicrofabricated ultrasound transducer probe.

According to an aspect of the application, an apparatus is providedcomprising a substrate, a plurality of ultrasonic transducers on thesubstrate, and control circuitry on the substrate, coupled to theplurality of ultrasonic transducers and configured to control operationof the plurality of ultrasonic transducers. The apparatus furthercomprises a first interface, the first interface being of a first type,and a second interface, the second interface being of a second type. Thefirst and second interfaces may be individually configured to transferelectronic signals between the control circuitry and an external device.

According to an aspect of the application, an apparatus is providedcomprising a single substrate ultrasound-on-a-chip imaging devicecomprising multiple different interface types supporting different datatransfer rates.

According to an aspect of the application, an apparatus is providedcomprising a substrate including a plurality of ultrasound elements, afirst interface of a first type on the substrate, and a second interfaceof a second type that is different than the first type on the substrate.

According to an aspect of the application, a method is provided,comprising forming a plurality of ultrasonic transducers on a substrate,forming control circuitry on the substrate, coupled to the plurality ofultrasonic transducers, and forming a first interface of a first type onthe substrate and a second interface of a second type on the substrate.The first and second interfaces may be individually configured toprovide an electrical connection between the control circuitry and anexternal device.

According to an aspect of the application, an apparatus is provided,comprising a substrate, a plurality of ultrasonic transducers on thesubstrate, and control circuitry on the substrate, coupled to theplurality of ultrasonic transducers and configured to control operationof the plurality of ultrasonic transducers. The control circuitrycomprises a waveform generator coupled to at least one ultrasonictransducer of the plurality of ultrasonic transducers, the waveformgenerator being configurable to generate different kinds of waveforms.

According to an aspect of the application, an apparatus is provided,comprising a substrate having a width and height, the width being atleast twice as large as the height, and a plurality of ultrasonictransducers on the substrate. The apparatus further comprises controlcircuitry on the substrate, coupled to the plurality of ultrasonictransducers and configured to control operation of the plurality ofultrasonic transducers.

According to an aspect of the application, an apparatus is provided,comprising a plurality of ultrasound transducer probes tiled andinterconnected to form an ultrasound imaging device. Each ultrasoundtransducer probe of the plurality of ultrasound transducer probesincludes a plurality of ultrasonic transducers and control circuitrycoupled to the plurality of ultrasonic transducers and configured tocontrol, at least in part, operation of the plurality of ultrasonictransducers. The control circuitry includes interface circuitryconfigured to interface the ultrasound transducer probe to an externaldevice.

According to an aspect of the application, an apparatus is provided,comprising at least one substrate having a first dimension and a seconddimension that is perpendicular to the first dimension. The firstdimension is at least twice as great as the second dimension. Theapparatus further comprises a plurality of ultrasonic transducers on thesubstrate, the plurality of ultrasonic transducers being arranged alongthe first dimension and the second dimension of the substrate. Theapparatus further comprises control circuitry coupled to the pluralityof ultrasonic transducers and configured to control operation of theplurality of ultrasonic transducers.

According to an aspect of the application, a method of forming anultrasound device is provided, comprising dicing at least first andsecond ultrasound transducer probes of a plurality of ultrasoundtransducer probes on a wafer, and tiling and interconnecting the atleast first and second ultrasound transducer probes.

According to an aspect of the application, a device is providedcomprising a plurality of complementary metal oxide semiconductor (CMOS)ultrasound transducer elements, and CMOS control circuitry coupled tothe plurality of CMOS ultrasound transducer elements and configured tocontrol the CMOS ultrasound transducer elements to supportone-dimensional (1D), two-dimensional (2D), and three-dimensional (3D)ultrasound imaging.

According to an aspect of the present application, a complementary metaloxide semiconductor (CMOS) integrated circuit (IC) is providedcomprising an array of ultrasound transducer elements and CMOS controlcircuitry coupled to the array of ultrasound transducer elements andconfigured to control operation of the array of ultrasound transducerelements to support both two-dimensional (2D) and three-dimensional (3D)ultrasound imaging.

According to an aspect of the application, an apparatus is provided,comprising a complementary metal oxide semiconductor (CMOS) substrateand a plurality of ultrasonic transducers on the CMOS substrate. Theapparatus further comprises a CMOS integrated circuit (IC) on the CMOSsubstrate and coupled to the plurality of ultrasonic transducers,wherein the CMOS IC is configured to support a voltage signal that isgreater than approximately 20 V.

According to an aspect of the application, an apparatus is provided,comprising a complementary metal oxide semiconductor (CMOS) substratehaving a top metal layer configured to conduct a power signal. Theapparatus further comprises an ultrasonic transducer disposed above thetop metal layer and including an electrode, wherein the electrode isconnected to the top metal layer by an electrically conductive via.

According to an aspect of the application an apparatus is providedcomprising a complementary metal oxide semiconductor (CMOS) substratehaving a top metal layer. The top metal layer has a thickness betweenapproximately 0.5 microns and approximately 10 microns. The apparatusfurther comprises an ultrasonic transducer disposed above the top metallayer.

According to an aspect of the application, an apparatus is providedcomprising a complementary metal oxide semiconductor (CMOS) substratehaving a metal layer having a thickness between approximately 0.5microns and approximately 10 microns. The apparatus further comprises anultrasonic transducer having an electrode. The apparatus furthercomprises a via connecting the electrode to the metal layer of the CMOSsubstrate.

According to an aspect of the application, an apparatus is providedcomprising a complementary metal oxide semiconductor (CMOS) substratecomprising a metallization layer and a wiring line. The apparatusfurther comprises an ultrasonic transducer on the CMOS substrate. Themetallization layer is configured to distribute a power signal and isconfigured as an electrical shield between the ultrasonic transducer andthe wiring line.

According to an aspect of the application, an apparatus is provided,comprising a complementary metal oxide semiconductor (CMOS) substrateand an ultrasonic transducer on the CMOS substrate. The ultrasonictransducer comprises a membrane sealing a cavity in the CMOS substrateand further comprises a thin film electrode. The cavity is between thethin film electrode and the membrane.

According to an aspect of the application, a method of fabricating anultrasonic transducer is provided, comprising forming the ultrasonictransducer above a top metal layer of a complementary metal oxidesemiconductor (CMOS) substrate, and connecting the ultrasonic transducerto the top metal layer with at least one electrically conductive via.

According to an aspect of the application a method of manufacturing anultrasonic transducer is provided, comprising forming a complementarymetal oxide semiconductor (CMOS) substrate, the CMOS substrate includinga metal layer, and forming an electrically conductive via through aportion of the CMOS substrate. The method further comprises forming theultrasonic transducer above the CMOS substrate, wherein at least aportion of the ultrasonic transducer is electrically coupled to the CMOSsubstrate through the electrically conductive via.

According to an aspect of the application, a method is provided,comprising printing a photolithography pattern on a wafer, rotating thewafer by approximately 180 degrees after printing the photolithographypattern on the wafer, and printing a copy of the photolithographypattern on the wafer after rotating the wafer by approximately 180degrees such that the pattern on the wafer and the copy of the patternon the wafer are aligned with each other.

According to an aspect of the application, a method is providedcomprising printing a photolithography pattern on a wafer, rotating thewafer after printing the photolithography pattern on the wafer, andprinting a copy of the photolithography pattern on the wafer afterrotating the wafer such that the pattern on the wafer and the copy ofthe pattern on the wafer are aligned with each other.

According to an aspect of the application, a method is provided,comprising illuminating a reticle having a pattern thereon to print apattern on a wafer, the pattern on the reticle having a first sidesubstantially opposite a second side, and the pattern on the waferhaving a first side substantially opposite a second side. The methodfurther comprises rotating the wafer approximately 180 degrees, andaligning the second side of the pattern on the reticle with the secondside of the pattern on the wafer. The method further comprises,subsequent to aligning the second side of the pattern on the reticlewith the second side of the pattern on the wafer, illuminating thereticle.

According to an aspect of the application, a method is provided,comprising scanning a first portion of a reticle with aphotolithographic scanner to print a first pattern on a wafer, the firstportion being less than the entire reticle. The method further comprisesstepping the wafer. The method further comprises, subsequent to steppingthe wafer, scanning a second portion of the reticle with thephotolithographic scanner to print a second pattern on the wafer inalignment with the first pattern, the second portion being less than theentire reticle and being different than the first portion.

According to an aspect of the application, a method is providedcomprising tiling ultrasound transducer probes on a wafer by printingdifferent patterns from one or more reticles on the wafer. Printingdifferent patterns may comprise using a blade to obstruct at least aportion of at least one reticle during tiling.

According to an aspect of the application, a method is providedcomprising scanning a first portion of a pattern mask with a scanner toprint a first pattern on a wafer, the pattern mask including a first,second, third, and fourth alignment mark thereon. The first portionincludes an area between the first alignment mark and the thirdalignment mark. The method further comprises moving the wafer, andscanning a second portion of the pattern mask with the scanner to printa second pattern on the wafer in alignment with the first pattern. Thesecond portion includes an area between the second alignment mark andthe fourth alignment mark.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and embodiments of the application will be describedwith reference to the following figures. It should be appreciated thatthe figures are not necessarily drawn to scale. Items appearing inmultiple figures are indicated by the same reference number in all thefigures in which they appear.

FIGS. 1A-1D illustrate differing ultrasound transducer devices which maybe formed from a common repeatable ultrasound transducer probe,according to non-limiting embodiments of the present application.

FIGS. 2A and 2B illustrate non-limiting alternative embodiments of anultrasound transducer probe which may be configured to beinterconnectable with other such ultrasound transducer probes, accordingto non-limiting embodiments of the present application.

FIGS. 2C, 2F, and 2G illustrates ultrasound transducer probes which maybe formed by tiling and interconnecting multiple instances of theultrasound transducer probe of FIG. 2A, according to non-limitingembodiments of the present application.

FIGS. 2D and 2E illustrate ultrasound transducer probes which may beformed by tiling and interconnecting multiple instances of theultrasound transducer probe of FIG. 2B, according to non-limitingembodiments of the present application.

FIG. 3 is a block diagram of an ultrasound transducer probe which may beconfigured to be tiled and interconnected with other such ultrasoundtransducer probes, according to a non-limiting embodiment of the presentapplication.

FIGS. 4A and 4B illustrate packaged ultrasound transducer probes withports providing access to different types of physical interfaces of theultrasound transducer probe, according to a non-limiting embodiment ofthe present application.

FIGS. 5A and 5B illustrate a non-limiting example of ultrasonictransducers (or transducer cells) arranged into transducer elements toform part of an ultrasound transducer probe, according to a non-limitingembodiment of the present application.

FIG. 5C illustrates different configurations of ultrasound elementswhich may be formed from a common arrangement of ultrasonic transducers.

FIG. 6 illustrates a cross-sectional view of an ultrasound transducerprobe having integrated circuitry beneath ultrasonic transducers of theultrasound transducer probe as well as integrated circuitry on aperipheral region of the ultrasound transducer probe, according to anon-limiting embodiment of the present application.

FIG. 7 is a schematic diagram illustrating the circuitry architecture ofan ultrasound transducer probe according to a non-limiting embodiment ofthe present application.

FIG. 8 illustrates a configuration of circuitry of an ultrasoundtransducer probe in which multiple ultrasound elements are associatedwith respective transmit excitation modules and share a receive module,according to a non-limiting embodiment of the present application.

FIG. 9 illustrates a non-limiting detailed implementation of theultrasound transducer probe of FIG. 7 in which the configuration of FIG.8 is implemented.

FIG. 10 illustrates the interconnection of transmit excitation modulesand a receive module for a plurality of ultrasound elements arranged ina column, according to a non-limiting embodiment of the presentapplication.

FIG. 11 illustrates an example of a programmable waveform generator of atype which may be used in an ultrasound transducer probe of the typesdescribed herein, according to a non-limiting embodiment of the presentapplication.

FIG. 12 illustrates a pulser of a type which may be used in anultrasound transducer probe of the types described herein, according toa non-limiting embodiment of the present application.

FIG. 13 illustrates an example of an ultrasound element coupled to apulser and to an amplifier according to a non-limiting embodiment of thepresent application.

FIG. 14 illustrates a clock circuit of a type which may be used in anultrasound transducer probe according to a non-limiting embodiment ofthe present application.

FIG. 15 illustrates a mesh which may be used to offload data from anultrasound transducer probe according to a non-limiting embodiment ofthe present application.

FIG. 16 is a detailed view of part of the mesh of FIG. 15, according toa non-limiting embodiment of the present application.

FIG. 17 illustrates a node configuration for the mesh of FIG. 15.

FIGS. 18A and 18B illustrate flowcharts of alternative manners ofoperating the mesh of FIG. 15, according to a non-limiting embodiment ofthe present application.

FIGS. 19-22 illustrate complementary metal oxide semiconductor (CMOS)transistor layouts for supporting high voltage operation, according tonon-limiting embodiments of the present application.

FIGS. 23, 24A, 24B, 25A, and 25B illustrate pulsers which are configuredto support high voltage operation and which may be used in ultrasoundtransducer probes of the types described herein, according to variousnon-limiting embodiments of the present application.

FIG. 26A illustrates an analog-to-digital converter (ADC) configured tosupport high voltage operation and which may be used in an ultrasoundtransducer probe according to a non-limiting embodiment of the presentapplication.

FIG. 26B is a timing diagram illustrating various signals relating tothe operation of the ADC of FIG. 26A.

FIG. 27 illustrates a sample and hold circuit configured to support highvoltage operation and which may be used in an ultrasound transducerprobe according to a non-limiting embodiment of the present application.

FIG. 28A illustrates a time-shared ADC which may be used in anultrasound transducer probe according to a non-limiting embodiment ofthe present application.

FIG. 28B illustrates a timing diagram of the operation of the ADC ofFIG. 28A.

FIG. 29A illustrates a circuit configuration including two pulserscoupled to an ultrasound element, according to a non-limiting embodimentof the present application.

FIG. 29B is a timing diagram of the operation of the pulsers of FIG.29A.

FIGS. 30A-30G illustrate a device including an ultrasonic transducerintegrated with a CMOS substrate and formed above a top metal layer ofthe CMOS substrate, and a method of fabricating the device, according toa non-limiting embodiment of the present application.

FIGS. 31A-31B illustrate a device including an ultrasonic transducerintegrated with a CMOS substrate, formed above a top metal layer of theCMOS substrate, and having a piston membrane and membrane stop, and amethod of fabricating the device, according to a non-limiting embodimentof the present application.

FIGS. 32A-32B illustrate another device including an ultrasonictransducer integrated with a CMOS substrate, formed above a top metallayer of the CMOS substrate, and having a piston membrane, and a methodof fabricating the device, according to a non-limiting embodiment of thepresent application.

FIG. 33 illustrates another device including an ultrasonic transducerintegrated with a CMOS substrate, formed above a top metal layer of theCMOS substrate, and having non-conductive cavity sidewalls, according toa non-limiting embodiment of the present application.

FIG. 34 illustrates another device including an ultrasonic transducerintegrated with a CMOS substrate, formed above a top metal layer of theCMOS substrate, and having a conductive via passing through a membraneof the ultrasonic transducer, according to a non-limiting embodiment ofthe present application.

FIG. 35 illustrates another device including an ultrasonic transducerintegrated with a CMOS substrate, formed above a top metal layer of theCMOS substrate, and having a topside conductive contact, according to anon-limiting embodiment of the present application.

FIG. 36 illustrates a device including the ultrasonic transducer of FIG.30A connected to an integrated circuit in the CMOS substrate, with theintegrated circuit disposed beneath the ultrasonic transducer.

FIG. 37 illustrates a block diagram of a process for fabricating anultrasonic transducer on a CMOS wafer, according to a non-limitingembodiment of the present application.

FIG. 38 illustrates the use of a reticle to perform horizontal tiling ofan ultrasound transducer probe, according to a non-limiting embodimentof the present application.

FIG. 39 illustrates a reticle having features at least partiallydefining input/output (I/O) circuitry of an ultrasound transducer probeon opposing sides of the reticle, according to a non-limiting embodimentof the present application.

FIGS. 40 and 41 illustrate ultrasound transducer probes that can beformed by horizontal tiling of a photolithography mask pattern,according to non-limiting embodiments of the present application.

DETAILED DESCRIPTION Overview

Aspects of the present application provide a microfabricated ultrasoundtransducer probe which may represent a universal building block toconstruct various types of ultrasound imaging and/or HIFU devicesoperable in various modes by mere replication and suitable connection ofmultiple copies of the transducer probe. In some embodiments, theultrasound transducer probe is suitable to operate as a standaloneultrasound transducer probe. One-dimensional (1D), one and a halfdimensional (1.5D), two-dimensional (2D), and three-dimensional (3D)ultrasound imaging devices capable of implementing highly advancedultrasound imaging techniques may be fabricated easily by replicationof, suitable dicing of, and interconnection of the ultrasound transducerprobe, with minimal or no redesign of the ultrasonic transducers andintegrated circuitry of the ultrasound transducer probe. As a result,the ultrasound transducer probe is highly versatile, providingflexibility in achieving an ultrasound device of choice.

Various features of the microfabricated ultrasound transducer probe maycontribute to its versatility and provide flexibility to an end user.One such feature is the inclusion of multiple types of interfaces forelectrically connecting to different types of external devices. In someembodiments, higher speed and lower speed interfaces may be provided aspart of the ultrasound transducer probe for communicating electricalsignals with external devices at different rates. The higher speedinterface(s) may facilitate connection of the ultrasound transducerprobe to any desired external processing device, such as specializedfield programmable gate arrays (FPGA), graphics processing units (GPU),or other devices suitable for receiving and processing ultrasound data,for example to form one or more ultrasound images. The higher speedinterface(s) may be configured in some embodiments to maximize theoutput of ultrasound data, which may be in digital form, from theultrasound transducer probe. In some embodiments, then, the higher speedinterface(s) may be used when complex ultrasound applications are to beperformed, such as 3D ultrasound imaging. The lower speed interface(s),by contrast, may be configured in some embodiments to allow forconnection of the ultrasound transducer probe to a consumer electronicsdevice with lesser processing capabilities than some types of devices towhich the higher speed interface(s) may be connected, and thus may besuitable when performing ultrasound applications not requiring theamount of data provided by the higher speed interface(s). Suchfunctionality may make the ultrasound transducer probe usable by a widerange of end users who lack access to more sophisticated graphicsprocessing systems, thereby making an important medical diagnostic toolaccessible to a large number of people. Thus, the interfaceconfiguration of the ultrasound transducer probe may enhance thetransducer probe's versatility by allowing for connection to a widerange of external devices, and may provide a user flexibility inchoosing to which external device(s) to connect.

Other features of an ultrasound transducer probe which may be providedaccording to some aspects of the present application and which maycontribute to the transducer probe's versatility include the transducerprobe's physical form and the architecture of the transducer probecircuitry. The ultrasound transducer probe may be microfabricated on asubstrate (e.g., a chip, such as a semiconductor chip) having a geometrythat provides for a suitable aperture. In some embodiments, for example,the substrate may allow for a suitable one-dimensional (1D) aperture,for instance being wider than it is tall (e.g., a wide aspect ratiosubstrate). Such a form factor may allow the transducer probe tofunction suitably as a 1D imaging device for performing 2D imaging whileallowing for multiple replicas of the transducer probe to be tiledhorizontally and/or vertically to provide enhanced 2D or 3D imagingfunctionality. As used herein, “tiled” means arranged next to each otherto form, in combination, a larger device. In some embodiments, theultrasound transducer probe may be a 1.5D device capable of tiling toprovide enhanced 2D or 3D imaging functionality.

Interconnection of multiple tiled replicas of the ultrasound transducerprobe in a manner suitable to form a larger ultrasound transducer probemay be facilitated by suitable relative physical positioning of theultrasonic transducers and integrated processing or control circuitry onthe substrate. As used herein, the term “control circuitry” may include,but is not limited to, circuitry that may control operation of theultrasonic transducers and/or processing circuitry that processessignals transmitted to and/or received from the ultrasonic transducers.In some embodiments, a portion of the control circuitry may bepositioned beneath an arrangement of ultrasonic transducers on thesubstrate, with other integrated circuitry including input/output (I/O)circuitry positioned on one or more peripheral regions (e.g., a tab insome embodiments) of the substrate. Such physical placement mayfacilitate tiling multiple copies of the ultrasound transducer probe byallowing for creation of a substantially continuous arrangement ofultrasonic transducers when tiled while providing suitable externalaccess to the circuitry of the transducer probes, i.e., not obstructingthe I/O circuitry when the transducer probes are tiled.

The integrated circuitry (e.g., integrated control circuitry) of theultrasound transducer probe may also facilitate interconnection of thetransducer probe with other such transducer probes, for example whentiled as described above. In some embodiments, the integrated circuitrymay be at least partially programmable, thus allowing for the ultrasoundtransducer probe to be programmed to operate as a standalone transducerprobe or in conjunction with one or more additional such transducerprobes. The programmable circuitry may include programmable timingcircuitry and/or a programmable waveform generator for generating (orproducing) excitation signals to excite the ultrasonic transducers. Thewaveform generator may be programmable to generate a desired kind ofwaveform from among multiple possible kinds, including impulses,continuous waves, chirp waveforms (e.g., linear frequency modulation(LFM)) chirps), and coded excitations. Such flexibility in the waveformgenerated may also facilitate the use of highly advanced ultrasoundimaging techniques, non-limiting examples of which are described furtherbelow.

The ultrasound transducer probe may include micromachined ultrasonictransducers having features which facilitate creation of a standaloneultrasound transducer probe, and which also facilitate formation ofultrasound devices by interconnection of multiple copies of theultrasound transducer probe. In some embodiments, the ultrasoundtransducer probe may be formed on a complementary metal oxidesemiconductor (CMOS) substrate. In some embodiments, the CMOS substratemay include a top metal layer, which in some embodiments may be a thicktop metal layer (also referred to in some embodiments as an ultra-thickredistribution layer), which may be utilized for power distribution tothe ultrasonic transducers. Such a configuration may facilitate suitablepower distribution to all ultrasonic transducers of the transducer probeover the relatively large distances which the power signal may travel insome embodiments. When the thick top metal layer is used for powerdistribution, the ultrasonic transducers may be formed above the thicktop metal layer, and may be connected to the thick top metal layer witha suitable electrically conductive via structure including one or moreelectrically conductive vias. In some such embodiments, one electricallyconductive via may connect a bottom electrode of an ultrasonictransducer to the thick top metal layer of the CMOS substrate, and asecond electrically conductive via may connect a membrane of theultrasonic transducer to the thick top metal layer. Further details ofsuch structures are described further below, along with methods offabricating such structures.

Some aspects of the present application provide wafer-level fabricationtechniques for fabricating ultrasound transducer probes of the typesdescribed herein. For example, interconnection of multiple copies of anultrasound transducer probe may be achieved in multiple ways accordingto different embodiments by suitable positioning of the ultrasoundtransducer probes on a wafer and suitable dicing. In some embodiments,multiple copies of the ultrasound transducer probes may be suitablytiled and interconnected on a wafer and then diced together to form asingle-substrate ultrasound device, for instance to meet certainperformance specifications for the device. In other embodiments,individual copies of the ultrasound transducer probe or groups ofmultiple instances of the ultrasound transducer probe may be diced froma wafer and interconnected after dicing. According to aspects of thepresent application, scanning and/or stepping technologies may be usedto suitably position multiple instances of an ultrasound transducerprobe on a wafer.

In some embodiments, multiple instances of an ultrasound transducerprobe may be aligned on a wafer by printing a pattern from a reticle onthe wafer, rotating the wafer, and printing the pattern again. In someembodiments, an ultrasound transducer probe may be formed by printingportions of a pattern from a reticle on the wafer in alignment with eachother. Blading techniques may be used to print desired portions of thereticle pattern, and stepping and/or scanning may be used to provideproper alignment of the various portions printed.

As described previously, some embodiments of the present applicationprovide an ultrasound transducer probe which may serve as a buildingblock (also referred to in some embodiments as a “repeatable unit” orsimply a “unit,” a “module,” or by other similar terminology) forconstructing ultrasound imaging devices with desired imagingcapabilities. In some such embodiments, the ultrasound transducer probemay be a 1D ultrasound transducer probe, but not all embodiments arelimited in this respect. For instance, the building block ultrasoundtransducer probe may be a 1.5D or 2D transducer probe in someembodiments.

The aspects and embodiments described above, as well as additionalaspects and embodiments, are described further below. These aspectsand/or embodiments may be used individually, all together, or in anycombination of two or more, as the application is not limited in thisrespect.

Standalone and Tiled Ultrasound Transducer Probes

According to an aspect of the present application, different types ofultrasound devices with different ultrasound imaging and/or HIFUcapabilities may be created utilizing a common, repeatable ultrasoundtransducer probe, which in some embodiments may be a 1D ultrasoundtransducer probe or a 1.5D ultrasound transducer probe. FIGS. 1A-1Dillustrate examples of ultrasound devices that may be created in thismanner.

FIG. 1A illustrates an ultrasound device 100 positioned to performultrasound analysis of a subject 102. The ultrasound device 100 mayrepresent a single repeatable ultrasound transducer probe. That is, theultrasound device 100 may be referred to alternatively as an ultrasoundtransducer probe. The ultrasound device 100 is connected to an externaldevice 104, illustrated as a smartphone (or mobile phone) in thisnon-limiting example, via a wired connection 106.

The ultrasound device 100 may be a 1D ultrasound transducer probe,configured with a 1D aperture formed by a plurality of ultrasonictransducers which may be microfabricated on a substrate (e.g., asemiconductor substrate in some embodiments). The ultrasound device 100may further include control circuitry configured to control, at least inpart, the ultrasonic transducers. Non-limiting examples of suitable 1Dultrasound transducer probes which may serve as the ultrasound device100 are described in further detail below, for example in connectionwith FIGS. 2A and 2B.

The ultrasound device 100 may have any suitable dimensions, including awidth W1 and height H1. In some embodiments, the ultrasound device 100may be a 1D ultrasound transducer probe configured with a 1D aperture,and thus the width W1 may be greater than the height H1 in some suchembodiments. In some embodiments, the width W1 may be betweenapproximately 20 mm and approximately 40 mm, or any value within thatrange. In some embodiments, the height H1 may be between approximately 2mm and approximately 10 mm, or any value within that range. In someembodiments, a square ultrasound device 100 may be provided having awidth W1 equal to the height H1.

The external device 104 may be a device configured to receive andprocess ultrasound data provided by the ultrasound device 100. In someembodiments, the external device 104 may be a consumer electronicsdevice (e.g., the illustrated smartphone) having a display 108 fordisplaying ultrasound data and/or ultrasound images based on ultrasounddata produced by the ultrasound device 100. However, other types ofexternal devices may be utilized as the various aspects described hereinare not limited to the particular type of external device to which theultrasound transducer probe is connected.

FIG. 1B illustrates a variation on FIG. 1A in which an ultrasound device110 is provided. The ultrasound device 110 may represent a compositeultrasound transducer probe including multiple repeatable ultrasoundtransducer probes, for example of the type illustrated in FIG. 1A. Theultrasound device 110 may be a 1D ultrasound transducer probe formed bysuitable horizontal tiling and interconnection of two of the ultrasounddevices 100 of FIG. 1A in a side-by-side (or left-to-right)configuration. Thus, the ultrasound device 110 may have the same heightH1 as the ultrasound device 100, but may have a width W2 that isapproximately or substantially twice as great as the width W1. In thismanner, the ultrasound device 110 may provide a greater linear aperturethan the ultrasound device 100 and may be used to image a greater area.

The ultrasound device 110 may be connected to an external device 112 viathe wired connection 106. In the example shown, the external device 112is a tablet computer having a display 114 for displaying ultrasound dataand/or ultrasound images based on ultrasound data produced by theultrasound device 110. However, other types of external devices may beused.

FIG. 1C illustrates a further example of an ultrasound device which maybe formed from a collection of multiple ultrasound transducer probes,for example of the type of ultrasound device 100 of FIG. 1A. That is,like the ultrasound device 110, the ultrasound device 116 may representa composite ultrasound transducer probe including multiple repeatableultrasound transducer probes, for example of the type illustrated inFIG. 1A.

The ultrasound device 116 may be a 2D ultrasound transducer probe formedby suitable vertical tiling (also referred to herein as “stacking”) andinterconnection of multiple copies of the ultrasound device 100. Thus,the ultrasound device 116 may have the same width W1 as ultrasounddevice 100 and a height H2 greater than the height H1 of ultrasounddevice 100. The height H2 may be, for example, N×H1, wherein Nrepresents the number of ultrasound devices 100 tiled vertically tocreate the ultrasound device 116. In some embodiments, N may equal 2, 4,8, may be between 2 and 10, or may assume any other suitable integervalue.

The ultrasound device 116 may be connected to an external device 118 bythe wired connection 106. The external device 118 may be any suitableexternal device, including any suitable consumer electronics device. Inthe non-limiting example illustrated, the external device 118 is alaptop computer having a display 120 for displaying ultrasound dataand/or ultrasound images based on ultrasound data produced by theultrasound device 116.

Although not shown, it should be appreciated that an ultrasound devicemay be constructed from horizontal and vertical tiling of multiplecopies of the ultrasound device 100, thus effectively representing acombination of ultrasound device 110 and ultrasound device 116. Forexample, two of the ultrasound devices 100 may be tiled horizontally,defining a “row” that is two ultrasound transducer probes wide, and twoor more such rows of two ultrasound transducer probes may be tiledvertically (e.g., 2 such rows, 4 such rows, 8 such rows, or any othersuitable number of such rows). Thus, an ultrasound transducer probehaving a desired size and aperture may be easily created by suitabletiling of an ultrasound transducer probe like ultrasound device 100. Theultrasound device 100 may therefore serve as a (universal) buildingblock for building an ultrasound device with target size and aperturecharacteristics, and therefore specified imaging and/or HIFUcapabilities.

A further example of an ultrasound device which may be formed utilizingmultiple copies of the ultrasound device 100 of FIG. 1A is shown in FIG.1D. As shown, the ultrasound device may include two copies of theultrasound device 116 of FIG. 1C, each of which may include two or moreinstances of the ultrasound device 100, as previously described. The twoultrasound devices 116 in FIG. 1D may be configured to operate incombination to perform transmissive ultrasound imaging, for examplebeing positioned on opposite sides of the subject 102. For example, theultrasound devices 116 may operate together in the configuration of FIG.1D according to the transmissive ultrasound operating techniquesdescribed in PCT Patent Application Publication No. WO 2013/059,358 A2,which is hereby incorporated herein by reference in its entirety. Theconfiguration of FIG. 1D may be particularly advantageous for 3Dultrasound imaging purposes, though it need not be used in this manner.

The ultrasound devices 116 in FIG. 1D may be connected to an externaldevice 122 via respective wired connections 124. The external device 122may be any suitable external device for receiving and processing theultrasound data provided by the ultrasound devices 116. In someembodiments, the external device 122 may include an FPGA, a GPU, orother suitable processing circuitry for receiving and handling largeamounts of ultrasound data as may be produced in the configuration ofFIG. 1D.

Also provided in FIG. 1D is a second external device 126 having adisplay 128 for displaying ultrasound data and/or ultrasound imagesbased on ultrasound data produced by the ultrasound devices 116. Theexternal device 126 may be connected to receive data from the externaldevice 122 in some embodiments, though alternative configurations arepossible. Furthermore, in some embodiments the external device 122 mayitself include a suitable display, and external device 126 may beomitted.

Thus, FIGS. 1A-1D illustrate different ultrasound transducer probes anddevice configurations for producing ultrasound data and/or ultrasoundimages based upon a common underlying ultrasound device 100. Bothreflective (e.g., FIGS. 1A-1C) and transmissive (e.g., FIG. 1D)ultrasound imaging devices may be created, operating in two or threedimensions.

The ultrasound devices illustrated in FIGS. 1A-1D and, more generally,described herein may be placed at various positions relative to asubject. In some embodiments, the ultrasound devices may be placed incontact with the subject. In some embodiments, the ultrasound devicesmay be placed in proximity to, but not in contact with, the subject, forexample being within several centimeters of the subject. Thus, theultrasound devices are not limited to being used at any particulardistance from a subject unless otherwise stated. Moreover, theultrasound devices may be moveable (or positionable), for example byhand. Thus, an operator (e.g., an ultrasound technician) may move thelocation of the ultrasound devices during operation, in someembodiments. The ultrasound devices may therefore be considered portablein some embodiments.

It should be appreciated that the ultrasound transducer probes shown inFIGS. 1A-1D may be considered ultrasound peripherals, configured to beconnected to (e.g., plugged into) a suitable external device to providesome control and/or processing functionality. Thus, aspects of thepresent application provide desired ultrasound peripherals based onsuitable replication and interconnection of a common, repeatableultrasound transducer probe design.

FIGS. 1A-1D illustrate ultrasound transducer probes connected toexternal devices by wired connections (e.g., wired connections 106 and124). However, wireless connections may alternatively be implemented insome embodiments.

FIGS. 2A-2G illustrate examples of configurations of ultrasoundtransducer probes which may be used to form the devices of FIGS. 1A-1D.FIG. 2A illustrates a first non-limiting example of an ultrasoundtransducer probe 200 representing an implementation of the ultrasounddevice 100. The ultrasound transducer probe 200 may be a 1D ultrasoundtransducer probe having a substrate 202 with the width W1 and height H1,on which a plurality of ultrasonic transducers 204 and integratedcontrol circuitry (not explicitly shown) are formed. As shown, theplurality of ultrasonic transducers 204 may be positioned over amajority of the substrate 202, including over the center of thesubstrate 202. A peripheral region 206 of the substrate 202, which mayrepresent a “tab” of the substrate 202, may include integrated circuitryincluding interface circuitry (e.g., interfaces 208 a and 208 b,described further below). The peripheral region 206 may not include anyof the ultrasonic transducers 204.

FIG. 2B illustrates a variation on the ultrasound transducer probe 200of FIG. 2A. The ultrasound transducer probe 210 of FIG. 2B may differfrom the ultrasound transducer probe 200 in that instead of a singleperipheral region 206, the ultrasound transducer probe 210 may includetwo peripheral regions (or “tabs”) 212 a and 212 b. The peripheralregions 212 a and 212 b may have a combined width, in the directionparallel to W1, equal to the width of peripheral region 206 in thedirection parallel to W1, though not all embodiments are limited in thisrespect. For example, each of regions 212 a and 212 b may have a widthin the direction parallel to W1 equal to approximately half the width ofperipheral region 206 in the direction parallel to W1. One or both ofthe peripheral regions 212 a and 212 b may include integrated circuitryincluding interface circuitry (not shown). In some embodiments, only oneof the two peripheral regions 212 a and 212 b may include I/O circuitryacting as an interface for an external device. Such a configuration mayfacilitate horizontal tiling of ultrasound transducer probes so thataccess to the integrated circuitry of the horizontally tiled ultrasoundtransducer probes need not be provided at a middle point between thehorizontally tiled transducer probes.

As previously described, the width W1 and height H1 may assume anysuitable values. In some embodiments, the aspect ratio of the substrate202, defined as the width relative to the height, may be greater than orequal to 1.5:1, greater than or equal to 2:1, greater than or equal to3:1, greater than or equal to 4:1, greater than or equal to 5:1, between2:1 and 16:1, between 4:1 and 10:1, or any range or value within suchranges, as non-limiting examples. The substrate 202 may be said to be awide aspect ratio substrate when the aspect ratio is greater than orequal to 3:1. In some embodiments, the width W1 may be betweenapproximately 20 mm and approximately 40 mm, or any value within thatrange. In some embodiments, the height H1 may be between approximately 2mm and approximately 10 mm, or any value within that range. As anon-limiting example, the width W1 may be approximately 32 mm and theheight H1 may be approximately 4 mm. In FIG. 2A, the width of theperipheral region 206, parallel to W1, may be approximately 3 mm withthe remaining part of the width of the ultrasound transducer probe 200being covered by ultrasonic transducers. In the embodiment of FIG. 2B,each of the peripheral regions 212 a and 212 b may have a width(parallel to W1) of approximately 1.5 mm.

It should be appreciated that the ultrasound transducer probes 200 and210 may be 1.5D ultrasound transducer probes in some embodiments. Forexample, a suitable number of ultrasonic transducers may be providedalong the height H1 to allow for focusing of ultrasound energy in theheight dimension.

FIG. 2C illustrates an ultrasound transducer probe 220 which mayrepresent an implementation of ultrasound device 110 of FIG. 1B. Asshown, the ultrasound transducer probe 220 may include two copies of theultrasound transducer probe 200 horizontally tiled, with the peripheralregions 206 positioned to be on opposite sides of the ultrasoundtransducer probe 220. The configuration of FIG. 2C may be achieved byfabricating the two copies of ultrasound transducer probe 200 on asingle wafer and dicing them together, or may be achieved byindividually dicing the two copies of ultrasound transducer probe 200and then positioning and interconnecting them. In some embodiments, onecopy of the ultrasonic transducer probe may be a mirror image of theother copy (e.g., the copy on the left side of transducer probe 220 maybe a mirror image of the copy on the right side of transducer probe220). Thus, aspects of the present application provide for suitabletiling of multiple instances of an ultrasound transducer probe in amirror image configuration to form a larger ultrasound transducer probe.

FIG. 2D illustrates an ultrasound transducer probe 230 which mayrepresent an implementation of ultrasound device 116 of FIG. 1C. Asshown, the ultrasound transducer probe 230 may include four copies ofthe ultrasound transducer probe 210 of FIG. 2B vertically tiled (alsoreferred to herein as “stacked”). The configuration of FIG. 2D may beachieved by fabricating the four copies of ultrasound transducer probe210 on a single wafer and dicing them together, or may be achieved bydicing one or more of the ultrasound transducer probes 210 individuallyand then positioning and interconnecting them.

FIG. 2E illustrates an alternative ultrasound transducer probe 240 whichmay represent an alternative implementation of ultrasound device 116 ofFIG. 1C. As shown, the ultrasound transducer probe 240 may include eightcopies of the ultrasound transducer probe 210 of FIG. 2B verticallytiled. The configuration of FIG. 2E may be achieved by fabricating theeight copies of ultrasound transducer probe 210 on a single wafer anddicing them together, or may be achieved by dicing one or more of theultrasound transducer probes 210 individually and then suitablypositioning and interconnecting them.

FIG. 2F illustrates an ultrasound transducer probe formed by suitablehorizontal and vertical tiling and interconnection of multiple instancesof the ultrasound transducer probe 200 of FIG. 2A. Namely, theultrasound transducer probe 250 includes four vertically tiled (orstacked) instances of the ultrasound transducer probe 220 of FIG. 2C,and thus includes eight instances of the ultrasound transducer probe 200of FIG. 2A. Four instances of the ultrasound transducer probe 200 may bepositioned on the left half of the ultrasound transducer probe 250, withthe other four instances of the ultrasound transducer probe 200 beingpositioned on the right half, as mirror images of the left half, ofultrasound transducer probe 250.

FIG. 2G illustrates a further example of an ultrasound transducer probewhich may be formed by suitable horizontal and vertical tiling andinterconnection of multiple instances of the ultrasound transducer probe200 of FIG. 2A. The ultrasound transducer probe 260 includes eightvertically tiled (or stacked) instances of the ultrasound transducerprobe 220 of FIG. 2C, and thus includes sixteen instances of theultrasound transducer probe 200.

It should be appreciated from FIGS. 2A-2G that suitable horizontaland/or vertical tiling of copies of an ultrasound transducer probeconfigured as a repeatable building block ultrasound transducer probemay be used to produce ultrasound transducer probes of variousdimensions. In this manner, the use of a common, repeatable ultrasoundtransducer probe design may simplify design and manufacture of multipledifferent ultrasound transducer probe configurations.

It should be appreciated that alternative configurations of a repeatableultrasound transducer probe to those shown in FIGS. 2A and 2B arepossible, still allowing for constructions of tiled devices like thoseillustrated in FIGS. 2C-2G. For example, an ultrasound transducer probemay include peripheral regions on the top and bottom sides of thesubstrate in addition to or as an alternative to the peripheral regions206, 212 a and 212 b. For example, peripheral regions free of ultrasonictransducers may be provided parallel to the length W1. Such peripheralregions may include only contact pads for making electrical connectionto the ultrasonic transducers in some embodiments, although inalternative embodiments circuitry may also be included. In someembodiments, an ultrasound transducer probe may include one or moreperipheral regions parallel to the width W1 and one or more peripheralregions parallel to the height H1. Such transducer probes may still betiled to form a contiguous region of ultrasonic transducers usingblading techniques of the type described further below, as an example.

FIG. 3 is a block diagram representation of an ultrasound transducerprobe which may serve as a stand-alone ultrasound transducer probe(e.g., a stand-alone 1D or 1.5D ultrasound transducer probe) and whichmay be repeatable so that it may be tiled and interconnected with othersuch transducer probes to form larger ultrasound devices. Thus, theultrasound transducer probe 300 is a block diagram of a non-limitingexample of the ultrasound device 100 of FIG. 1A and ultrasoundtransducer probes 200 and 210 of FIGS. 2A and 2B, respectively.

As shown, the ultrasound transducer probe 300 may include a substrate302 on which may be a plurality of ultrasonic transducers 304 andintegrated circuitry 306, which may perform control and/or processingfunctions. Interfaces 308 a and 308 b may provide electricalcommunication between the ultrasound transducer probe 300 and anexternal device (e.g., any of the external devices illustrated in FIGS.1A-1D).

The ultrasonic transducers 304 may be capacitive micromachinedultrasonic transducers (CMUTs), CMOS ultrasonic transducers (CUTs),which are monolithically integrated ultrasonic transducers and CMOS ICs,or other ultrasonic transducers compatible with a CMOS substrate. Insome embodiments, the ultrasonic transducers 304 may be formed on thesubstrate 302 using microfabrication techniques, and in some embodimentsmay be monolithically integrated with the substrate 302. For example,the substrate 302 may be a CMOS substrate and the ultrasonic transducers304 may be monolithically integrated with the CMOS substrate.

The plurality of ultrasonic transducers 304 may be arranged to form a 1D(or 1.5D) aperture on the substrate 302, and the integrated circuitry306 may operate the plurality of ultrasonic transducers in a 2D mode.The integrated circuitry may, in such an example, include transmit andreceive circuitry. The ultrasound transducer probe 300 may be consideredan ultrasound system-on-a-chip in some embodiments.

Various features of the ultrasound transducer probe 300, as well asultrasound transducer probes 200 and 210 are now described in furtherdetail.

Interface

Aspects of the present application provide an ultrasound transducerprobe having multiple types of interfaces for electrically connectingthe transducer probe to external devices via corresponding wired orwireless links. For example, higher speed and lower speed interfaces maybe provided to allow an end user flexibility in choosing a type ofdevice to which to connect the ultrasound transducer probe. FIG. 3provides a non-limiting example.

The interfaces 308 a and 308 b may represent physical interfaces and maybe considered part of the integrated circuitry 306. They may provide forelectrical communication between the ultrasound transducer probe 300 andan external device. In some embodiments, the interfaces 308 a and 308 bmay be of different types, configured to connect to different types ofexternal devices. For example, the interface 308 a may be of a typeconfigured to connect to external devices capable of receiving andprocessing large amounts of ultrasound data, such as a specialized FPGA,a GPU, or other suitable device. By contrast, the interface 308 b may beconfigured to operate with more widely available communication protocolsused for consumer electronics devices, such as universal serial bus(USB) connections. Accordingly, the ultrasound transducer probe 300 maybe highly versatile, allowing for the highest possible performance viaconnection to an external device with interface 308 a or allowing foruse with widely accessible consumer electronics via interface 308 b,thus expanding the accessibility of ultrasound technology compared tocurrent devices. The end user may choose between which interface to usein some embodiments.

When the interfaces 308 a and 308 b represent different types ofphysical interfaces, they may differ in the communication protocolssupported and/or the speed of data communication supported (i.e., thedata rate supported). For example, interface 308 a may be a higher speedinterface while interface 308 b may be a lower speed interface. Thus,the interface 308 a may be configured to maximize the amount of datawhich the ultrasound transducer probe 300 may provide to an externaldevice, and thus may be used in situations in which advanced ultrasoundimaging techniques are desirably implemented, high resolution isdesired, fast frame rates are desired, or other imaging characteristicsfacilitated by high speed communication are desired. In someembodiments, a high speed interface may support data rates aboveapproximately 4 gigabits per second (Gbps), above approximately 5 Gbps,above approximately 9 Gbps, above approximately 10 Gbps, aboveapproximately 12 Gbps, above approximately 15 Gbps, above 30 Gbps,between approximately 9 Gbps and approximately 100 Gbps, between 15 Gbpsand 50 Gbps, any data rate within those ranges, or any other suitabledata rate. These data rates may represent maximum data rates in someembodiments.

By comparison, the interface 308 b may be a relatively low speedinterface suitable for supporting communication with consumerelectronics (e.g., a portable device) or other external devices whichmay not be capable of performing the same level of ultrasound dataprocessing as that provided by external devices connectable to theinterface 308 a, but which may be more widely available. When theinterface 308 b represents a relatively low speed interface, it maysupport less sophisticated ultrasound imaging techniques, may providelower resolution ultrasound data, may provide lower frame rates, orotherwise provide a decrease in performance compared to that provided byinterface 308 a. In some embodiments, the interface 308 b may beconfigured to support data rates less than approximately 10 Gbps, lessthan approximate 5 Gbps, less than approximately 4 Gbps, less thanapproximately 3 Gbps, less than approximately 2 Gbps, any data ratewithin those ranges, or any other suitable data rate. These data ratesmay represent maximum data rates in some embodiments.

Non-limiting examples of high speed interfaces, for example which mayserve as interface 308 a, include twisted pair interfaces, low voltagedifferential signaling (LVDS) interfaces, and optical fiber interfaces.Such high speed interfaces may implement high speed protocols such asSerDES, SONET, 10 GB Ethernet, 40 GB Ethernet, 100 GB Ethernet, PCIExpress, HDMI, Infiniband, Thunderbolt, and JESD-204B, among others.External devices to which such an interface may connect may include highthroughput devices, such as high throughput FPGAs.

In some embodiments, a high speed interface of an ultrasound transducerprobe may connect to an FPGA which may perform some type of processing,such as packetization, compression, or other processing, before sendingsuch data to a digital signal processor (DSP), central processing unit(CPU), or GPU. In some embodiments, the suitability of an externaldevice for connection to a high speed interface of an ultrasoundtransducer probe (e.g., interface 308 a) may be quantified byconsidering minimum memory and processing capacity targets. For example,a suitable external device may include over approximately 2 GB of randomaccess memory (RAM) and/or over a particular number of processing cores,for example greater than 300 processing cores, greater than 400processing cores, greater than 500 processing cores, between 200 and 600processing cores, any number within that range, or any other suitablenumber. As non-limiting examples, the NVIDIA GTX 680 and NVIDIA TeslaK20, available from NVIDIA of Santa Clara, Calif., may be implemented insome embodiments as suitable external devices to which to connect a highspeed interface of an ultrasound transducer probe of the types describedherein.

Non-limiting examples of lower speed interfaces, for example which maybe used for interface 308 b, include USB 3.0, USB 2.0, firewire, andGigabit Ethernet. The lower speed interfaces may be capable ofconnection to an external device via only a single cable in someembodiments (e.g., a USB cable).

In those aspects of the present application in which an ultrasoundtransducer probe includes different types of physical interfaces forinterfacing with external devices, more than two different types ofinterfaces may be provided and/or more than two instances of one or moretypes of interfaces may be provided with an ultrasound transducer probe.For example, referring to FIG. 3, more than two interfaces may beprovided with the ultrasound transducer probe 300. Considering FIG. 2A,for instance, four higher speed interfaces 208 a may be provided whileonly a single lower speed interface 208 b may be provided. The 4:1 ratioillustrated is non-limiting, however. For example, the ratio of higherspeed interfaces to lower speed interfaces of an ultrasound transducerprobe may be 2:1, 4:1, 8:1, 10:1, 1:1, 1:2, 1:4, any suitable ratiobetween those listed (e.g., between 10:1 and 1:4), or any other suitableratio. More than one instance of the lower speed interface may also beprovided in some embodiments.

As previously described, the higher speed interfaces may be configuredto maximize the amount of ultrasound data provided by the ultrasoundtransducer probe to an external device. The number of higher speedinterfaces may be selected accordingly in some embodiments. The numberof higher speed interfaces may be selected based on the number ofreceive signal channels of the ultrasound transducer probe, which willbe described further below in connection with an example of thearchitecture of the ultrasound transducer probe. For example, the morereceive channels included with the ultrasound transducer probe, thegreater the number of higher speed interfaces which may be included. Insome embodiments, the number of higher speed interfaces provided mayscale linearly and proportionally with the number of receive channels ofthe ultrasound transducer probe.

When multiple interfaces of a single type are included on a transducerprobe of the types described herein, not all such interfaces need beused in all embodiments. The point may be illustrated by considerationof the ultrasound transducer probe 200 of FIG. 2A with the fourillustrated interfaces 208 a. In some embodiments, all four suchinterfaces may be utilized, for example when it is desired to maximizedata output from the ultrasound transducer probe. However, in someembodiments, a reduced number of the four illustrated interfaces 208 amay be used. For instance, only one, two, or three of the fourinterfaces 208 a may be used in some embodiments, even though thetransducer probe 200 may include all four. In some such embodiments, thenumber of interfaces used in operation may be dependent on a cableconnected to the interfaces, non-limiting examples of which aredescribed below in connection with FIGS. 4A and 4B. For example,plugging the transducer probe 200 into an external device using aparticular type of cable may dictate how many of the four interfaces 208a are used. In an alternative embodiment, the number of availableinterfaces of a given type which are used in operation of the transducerprobe may be programmable and thus a user may select the number via aselection tool (e.g., a menu option on a control program).

Although not explicitly shown, the interfaces of ultrasound transducerprobes 210, 220, 230, 240, 250, and 260 may also generally conform tothe configuration of the interfaces of ultrasound transducer probe 300,including both higher and lower speed interfaces. The ultrasoundtransducer probe 210 may include the same interfaces 208 a and 208 b ofultrasound transducer probe 200, located on the peripheral region(s) 212a and/or 212 b in some embodiments. For example, in a first embodiment,the peripheral region 212 a may include the interfaces of ultrasoundtransducer probe 200 of FIG. 2A (i.e., four higher speed interfaces 208a and one lower speed interface 208 b). In an alternative embodiment,the higher speed interfaces may be split (equally or not) between theperipheral region 212 a and the peripheral region 212 b. Otherconfigurations are also possible.

Because the ultrasound transducer probes 220, 230, 240, 250, and 260represent multiple instances of the ultrasound transducer probe 200 or210, the number of interfaces included may simply scale with the numberof instances of the ultrasound transducer probe 200 or 210 making up theultrasound transducer probes 220, 230, 240, 250, and 260.

The physical interfaces described herein may be suitable for wiredconnections (e.g., a cable) or wireless connection in some embodiments.Thus, the aspects of the present application relating to an ultrasoundtransducer probe having two or more different types of interfaces arenot limited to whether the interfaces are configured for wired orwireless connection unless otherwise stated.

When a wired connection is made to the interfaces of an ultrasoundtransducer probe of the types described herein, such connection may bemade in any suitable manner. In some embodiments, the ultrasoundtransducer probe may be enclosed within a package or housing, and one ormore ports may be provided for connecting a wire/cable to the ultrasoundtransducer probe. In some such embodiments, one port for each type ofinterface of the ultrasound transducer probe may be provided, thoughalternative configurations are possible. A non-limiting example isillustrated in FIG. 4A.

The device 400 of FIG. 4A represents a non-limiting example of anultrasound transducer probe 400 including a package 402 (also referredto herein as a “housing”). The package 402 may substantially enclose anultrasound transducer probe of the types illustrated in FIGS. 2A-2G. Theultrasound transducer probe 400 includes two ports, 404 a and 404 bwhich may allow for connection of respective cables to thepreviously-described interfaces 208 a and 208 b. For instance, port 404a may be configured to receive a cable connecting to interface 208 a andport 404 b may be configured to receive a cable connecting to interface208 b. The ports 404 a and 404 b may be any suitable types of ports foraccepting cables (or, more generally, wired connectors such as wiredconnections 106 and 124) for the types of interfaces implemented on theultrasound transducer probe.

As a non-limiting example, the port 404 b may be suitable for connectingto a USB cable (e.g., wired connection 106 or 124 may be a USB cable).As previously described, interface 208 b may, in some embodiments, be asuitable interface for connecting the ultrasound transducer probe to aconsumer electronics device. In some such embodiments, the interface 208b may be compatible with a USB connection, since many consumerelectronics devices are configured to connect to other devices via USBcables. Thus, the port 404 b may be a USB port. However, it should beappreciated that alternatives are possible.

As a non-limiting example, the port 404 a may be suitable for connectingto a direct-attach cable, such as a quad small form-factor pluggable(QSFP) cable (e.g., wired connection 106 or 124 may be a QSFP cable). Aspreviously described, the ultrasound transducer probe 200 may includemultiple interfaces 208 a (or, stated another way, multiple instances ofthe interface 208 a), yet in some embodiments only a single cable may beneeded to connect the interfaces to an external device, and thus only asingle port 404 a may be provided. For example, use of a QSFP cable mayallow for connection of a single cable to four of the interfaces 208 a.In this manner, the number of interfaces of the ultrasound transducerprobe to which any external device is connected may be determined by thecable used to connect the ultrasound transducer probe 400 to theexternal device, which may render transparent the process of selectinghow many interfaces to connect to.

In some embodiments, a single cable may be used for each interface ofthe ultrasound transducer probe to which an external device is to beconnected. In such instances, the ultrasound transducer probe 400 mayinclude a port corresponding to each of the physical interfaces 208 aand 208 b.

It should be appreciated that in operation the ultrasound transducerprobe 400 may be connected to an external device by a single cable at atime. That is, the user may select whether to utilize the interface 208a or the interface 208 b, and thus connect a single cable to theappropriate port 404 a or 404 b.

FIG. 4B illustrates an alternative ultrasound transducer probe 410 tothat of FIG. 4A. The ultrasound transducer probe 410 represents anon-limiting example of an ultrasound transducer probe including apackage and may represent a packaged version of ultrasound transducerprobe 220 of FIG. 2C, i.e., including two instances of the ultrasoundtransducer probe 200 of FIG. 2A. The ultrasound transducer probe 410includes a package (or housing) 412 and four ports 414 a-414 d. Two ofthe four ports (e.g., ports 414 a and 414 c) may be configured toconnect interfaces of the type of interface 208 a to an external devicevia a suitable cable, while the other two ports (e.g., ports 414 b and414 d) may be configured to connect interfaces of the type of interface208 b to an external device via a suitable cable. Thus, it should beappreciated that in operation the ultrasound transducer probe 410 may beconnected to an external device by two cables at a time, in someembodiments.

In some embodiments, the package or housing of an ultrasound device maylimit accessibility to one or more interfaces of the ultrasoundtransducer probe. The point may be illustrated by considering theultrasound transducer probe 200 of FIG. 2A, having interfaces 208 a and208 b. In some embodiments, the ultrasound transducer probe 200 may bepackaged with a package that has one or more ports providing access onlyto the interface 208 a, or alternatively only to the interface 208 b.Such a configuration may allow for production and distribution ofultrasound devices to target consumers without needing to change theunderlying design of transducer probe 200 (e.g., not all consumers maywant or need to have the option of connecting the ultrasound transducerprobe via the two or more types of interfaces).

Although some embodiments have been described in which multiple types ofinterfaces are provided with an ultrasound transducer probe, not allembodiments are limited in this respect. In some embodiments, only asingle type of interface may be provided on the probe. For example, insome embodiments, an ultrasound transducer probe like that of FIG. 2Amay lack the interface 208 a or 208 b.

Architecture

As previously described, various features of an ultrasound transducerprobe may facilitate use of the transducer probe as a stand-aloneultrasound transducer probe (e.g., a stand-alone or self-contained 1D,1.5D or 2D ultrasound transducer probe) or as a component of a largerultrasound device formed by tiling and interconnection of multipleinstances of the transducer probe. One such feature is the physicalarchitecture of the transducer probe, including the geometry of thetransducer probe and the positioning of ultrasonic transducers andintegrated circuitry of the transducer probe.

Form Factor of Ultrasound Transducer Probes

The geometry of the ultrasound transducer probe may be selected toprovide a desired aperture, which may facilitate tiling andinterconnection of multiple instances of the transducer probe to form alarger ultrasound device having a desired aperture. In some embodiments,an ultrasound transducer probe may have a first side longer than asecond side, where the first side is substantially perpendicular to thesecond side. The sides may represent sides of a device surface on whichultrasonic transducers and/or circuitry are formed. As an example, theultrasound device 100 of FIG. 1 has a first side representing a width W1and a second side representing a height H1. As previously described, W1may be greater than H1. FIGS. 2A and 2B also illustrate the point. Insome such embodiments, the transducer probe may be a wide aspect ratiotransducer probe. In some embodiments, the width to height ratio may begreater than or equal to 3:1, greater than or equal to 4:1, greater thanor equal to 5:1, greater than or equal to 10:1, between 2:1 and 15:1,between 4:1 and 10:1, any range or value within such ranges, or anyother suitable aspect ratio.

As has been described, in some embodiments an ultrasound transducerprobe includes a substrate, such as a semiconductor or CMOS substrate(e.g., substrate 202 of transducer probe 200). In any of thoseembodiments in which the transducer probe has one side longer thananother perpendicular side (e.g., when the transducer probe is a wideaspect ratio transducer probe), the dimensions may refer to thedimensions of the substrate.

Referring to FIG. 3, the substrate 302 may be any suitable substrate andin some embodiments may be a semiconductor substrate or CMOS substrate,such as a silicon substrate, a silicon-on-insulator (SOI) substrate, oran engineered substrate. In some embodiments, the substrate 302 may be aCMOS substrate suitable for supporting integrated circuitry, such asintegrated circuitry 306. Likewise, the substrate 202 of ultrasoundtransducer probe 200 may be any of those types of substrates listed.

In some embodiments the use of an ultrasound transducer probe having oneside longer than a perpendicular side (e.g., a wide aspect ratiotransducer probe) may provide benefits in terms of the aperture of thetransducer probe. For example, such a configuration may facilitatecreation of a suitable 1D transducer probe aperture. Thus, in someembodiments, the dimensions of an ultrasound transducer probe (e.g.,ultrasound transducer probes 200 and 210) may be selected to provide adesired aperture (e.g., a desired 1D aperture or 2D aperture). In someembodiments, a transducer probe having a width of between approximately30 mm and approximately 40 mm and having a height between approximately2 mm and approximately 8 mm may provide a suitable 1D aperture, allowingfor suitable focusing of an ultrasound beam in the height dimension.

The ultrasonic transducers of an ultrasound transducer probe may assumea configuration suitable for providing a desired aperture. For example,referring to FIG. 2A, the plurality of ultrasonic transducers 204 mayassume a configuration in which the transducers are arranged along agreater distance in the direction of the width W1 than in the directionof the height H1, and in some embodiments may be arranged suitably toprovide a desired 1D, 1.5D, or 2D aperture. In some embodiments, theplurality of ultrasonic transducers (e.g., ultrasonic transducers 204 or304) may be arranged in an array, though alternative arrangements arepossible.

One or more lensing components may be provided with the ultrasoundtransducer probe to control the focus of the ultrasound transducerprobe. For example, an acoustic lens may be provided overlying theultrasonic transducers to focus transmitted and/or received acousticsignals. The acoustic lens may assume any suitable configuration forproviding desired lensing functionality and may be formed of anysuitable material. For example, referring to FIGS. 4A and 4B, referencenumbers 416 and 418 may represent acoustic lenses. The acoustic lensesmay have a curved (e.g., convex) geometry when viewed in cross-section,in some embodiments. The curvature may be in the elevation dimension(e.g., in the direction of the height H1 referring to FIG. 2A, as anexample) in some embodiments, although curvature in other dimensions ora combination of two dimensions is possible.

Any suitable number of ultrasonic transducers may be provided on anultrasound transducer probe, as the number is not limiting of thevarious aspects described herein. In some embodiments, tens, hundreds,thousands, hundreds of thousands, or millions of ultrasonic transducersmay be provided on an ultrasound transducer probe. As a non-limitingexample, the plurality of ultrasonic transducers 204 of ultrasoundtransducer probe 200 may include an array of sixteen rows (parallel tothe width W1) of ultrasound elements with each row of ultrasoundelements having 128 ultrasound elements. The same may be true for theultrasound transducer probe 210 of FIG. 2B. Thus, ultrasound transducerprobe 220 of FIG. 2C may include sixteen rows of ultrasound elementswith each row having 256 ultrasound elements. Ultrasound transducerprobe 230 may include an array of 64 rows of ultrasound elements witheach row having 128 ultrasound elements. Ultrasound transducer probe 240may include an array of 128 rows of ultrasound elements with each rowhaving 128 ultrasound elements. Ultrasound transducer probe 250 mayinclude an array of 64 rows of ultrasound elements with each rowincluding 256 ultrasound elements. Ultrasound transducer probe 260 mayinclude 128 rows of ultrasound elements with each row including 256ultrasound elements. In any such embodiment, each ultrasound element mayhave one or more ultrasonic transducers. An example is now described inconnection with FIGS. 5A and 5B.

FIG. 5A replicates FIG. 2B with the addition of an enlarged inset 502.As shown in the inset 502, the ultrasound transducer probe 210 mayinclude sixteen rows (arranged along the height H1) of ultrasoundelements 504. The ultrasound transducer probe 210 may include 128columns of ultrasound elements 504 extending substantially across thewidth W1, except not covering the peripheral regions 212 a and 212 b.The ultrasound elements 504 are illustrated as being square, but neednot be in all embodiments.

In some embodiments, the ultrasound elements (e.g., element 504) mayinclude one or more ultrasonic transducers (also referred to herein as“transducer cells”). Stated differently, the ultrasonic transducers maybe grouped together to form ultrasound elements. The concept isillustrated in connection with cluster 506 of ultrasound elements 508a-508 d, enlarged in FIG. 5B. Referring to FIG. 5B, each of theillustrated ultrasound elements 508 a-508 d includes a 5×5 arrangementof ultrasonic transducers 510, though other arrangements and othernumbers of ultrasonic transducers may be included in an ultrasoundelement.

The ultrasonic transducers 510 may be CMUTs, CUTs, or other suitableultrasonic transducers. The ultrasonic transducers 510 are illustratedas being circular (from a top view) but may have any suitable geometry.The ultrasonic transducers 510 within an element 504 may be electricallyinterconnected to operate as a single element rather than asindividually controllable transducers. For example, the transducers mayhave one or more common electrodes to provide unified operation.

FIG. 5B illustrates a non-limiting example of the spacing of theultrasonic transducers 510 and the ultrasound elements 508 a-508 d. Theultrasonic transducers 510 may have diameters D1 of approximately 50microns, between approximately 30 microns and approximately 70 microns,any value within that range, or any other suitable diameter. The inset512, which provides an expanded view of a portion of ultrasound elements508 b and 508 d, shows that the ultrasound elements may be spaced by akerf k1 of approximately 10 microns (or any other suitable distance)such that the center-to-center distance L2 between ultrasonictransducers 510 of neighboring ultrasound elements 504 may be, forexample, approximately 60 microns. Providing such spacing betweenultrasound elements may allow for running signal lines between theelements and/or reducing acoustic cross-talk between the ultrasoundelements. However, in some embodiments the ultrasound elements may nothave any additional spacing between them other than the spacing betweenindividual ultrasonic transducers. As an example, the spacing betweenultrasound transducers 510 within an ultrasound element may beapproximately 2 microns.

The transducer cell pitch L1 of the ultrasonic transducers may beapproximately 52 microns or any other suitable value. The length L3 ofan ultrasound element of the type illustrated in FIG. 5B may beapproximately 258 microns or any other suitable value. The ultrasoundelement pitch L4 of neighboring ultrasound elements may be approximately268 microns or any other suitable value. It should be appreciated thatthe values of the distances shown in FIG. 5B are non-limiting, and thatalternative values for the element size, transducer size, cell andelement pitches, and the kerf are possible.

While FIG. 5B illustrates a non-limiting example of a configuration ofan ultrasound element including a 5×5 arrangement of ultrasonictransducers, variations are possible. In some embodiments, theconfiguration of ultrasonic transducers defining an ultrasound elementmay be configurable during manufacture of the device via choice of ametallization layer. That is, in some embodiments the ultrasonictransducers may be microfabricated and selection of a metal layerinterconnecting multiple ultrasonic transducers may be used to defineultrasound elements of a desired configuration. FIG. 5C illustrates anexample.

FIG. 5C illustrates a plurality of ultrasonic transducers 514. In thisexample, the ultrasonic transducers are laid out substantially in arepeating array of 4×4 blocks, which represents an example of aconfiguration of ultrasonic transducers on an ultrasound transducerprobe. From this arrangement of ultrasonic transducers, differentultrasound element configurations may be created via choice of ametallization layer. Three different potential ultrasound elementconfigurations are illustrated. Namely, a 4×4 element 516 may becreated. Alternatively a 2×8 element 518 may be created. As a thirdoption, a 1×16 element 520 may be created. Depending on theconfiguration chosen, the remaining ultrasonic transducers 514 may begrouped into similarly configured ultrasound elements. For example, allthe illustrated ultrasonic transducers 514 may be grouped into 4×4elements, or into 2×8 elements, or into 1×16 elements. These differingconfigurations may be formed with an underlying arrangement ofultrasonic transducers (e.g., the arrangement of ultrasonic transducers514) simply by patterning a metallization layer appropriately (i.e., inthe illustrated configurations) to serve as a common electrode for theultrasonic transducers within each element. Thus, configurability ofultrasound transducer elements may be provided during the manufacturingprocess.

Such configurability may be utilized to facilitate certain operatingmodes. Examples of ultrasound imaging modes which may be implemented byultrasound transducer probes according to aspects of the presentapplication are described further below. A particular ultrasound elementconfiguration (e.g., one of the configurations shown in FIG. 5C) may beutilized to facilitate implementation of a particular imaging mode.

The physical placement of the circuitry of an ultrasound transducerprobe of the types described herein may also facilitate the use of theultrasound transducer probe as a stand-alone ultrasound transducer probeor as a component of a larger transducer probe formed by tiling andinterconnection of multiple instances of the transducer probe. Aspreviously described, in some embodiments the ultrasound transducerprobe may include a CMOS substrate and integrated circuitry. In someembodiments, at least some circuitry of the ultrasound transducer probemay be positioned beneath the ultrasonic transducers of the transducerprobe. In some embodiments, some of the integrated circuitry may bepositioned on the peripheral region (or “tab”) of the ultrasoundtransducer probe. For instance, circuitry which is shared among two ormore of the ultrasonic transducers or ultrasound elements may bepositioned on the peripheral region. Yet, circuitry specific to anultrasound element or to a particular ultrasonic transducer may bepositioned beneath that ultrasound element or ultrasonic transducer insome embodiments. A non-limiting example is shown in FIG. 6.

Placement of Ultrasonic Transducers and Circuitry

FIG. 6 illustrates a simplified cross-sectional view of an ultrasoundtransducer probe having ultrasonic transducers and integrated circuitryon a substrate. For instance, FIG. 6 may represent a cross-section ofthe ultrasound transducer probe 200 of FIG. 2A taken into and out of thepage of FIG. 2A and along the width W1. As shown, the substrate 202 mayhave the plurality of ultrasonic transducers 204 formed thereon, whichmay be arranged in ultrasound elements. In some embodiments, theultrasonic transducers 204 may be integrated with (e.g., monolithicallyintegrated with) the substrate 202. For instance, the substrate 202 maybe a CMOS substrate and the ultrasonic transducers 204 may be CUTs orCMUTs monolithically integrated with the substrate 202.

As shown, the ultrasound transducer probe of FIG. 6 may further includeintegrated circuitry 602 and 604, which may be considered in someembodiments to form a single integrated circuit. The integratedcircuitry 602 and/or 604 may include circuitry for controlling operationof the ultrasonic transducers 204 (e.g., transmit and receive circuitry)and/or processing of signals received by the ultrasonic transducers(e.g., decimation and filtering) and/or for interfacing the ultrasoundtransducer probe with an external device (e.g., interfaces 208 a and 208b). As shown, the integrated circuitry 602 may be positioned (ordisposed or placed) beneath the ultrasonic transducers 204. Such aconfiguration may conserve chip area, allowing for the ultrasoundtransducer probe to be more compact than would be possible if theintegrated circuitry 602 was in-plane with the ultrasonic transducers204. The integrated circuitry 602 and the ultrasonic transducers 204 maybe connected in any suitable manner, non-limiting examples of which aredescribed further below, for example in connection with FIG. 36. Forexample, the integrated circuitry 602 and ultrasonic transducers 204 maybe connected by one or more vias between an ultrasonic transducer and ametallization layer of the substrate 202.

In some embodiments, the integrated circuitry 602 may be arranged intoIC cells corresponding to the ultrasonic transducers or to ultrasoundelements of the type described in connection with FIG. 5A. For example,transmit and/or receive circuitry specific to a particular ultrasonictransducer 204 or ultrasound element may be disposed beneath thatultrasonic transducer or element. As a non-limiting example, theintegrated circuitry 602 may include a low-noise amplifier (LNA) foreach ultrasound element of the ultrasound transducer probe, and each LNAmay be positioned beneath the respective ultrasound element. In someembodiments, a first transistor of the LNA may be positioned beneath therespective ultrasound element and the remainder of the LNA positionedelsewhere (e.g., in a peripheral region). The LNA may be atransimpedance amplifier (TIA) in some embodiments, and in others may bea transconductance amplifier, voltage amplifier, or current amplifier,as non-limiting examples. In some embodiments, a waveform generator foreach ultrasound element may be positioned beneath the ultrasoundelement.

As shown, the integrated circuitry 604 may be positioned on theperipheral region 206 (indicated as being to the left of the verticaldashed line). In some embodiments, the integrated circuitry 604 mayinclude circuitry which is not specific to any particular transducer ofthe ultrasound transducer probe. For example, timing circuitry, I/Ocircuitry, power conversion circuitry, or other circuitry which may beshared among multiple transducers or elements, or shared among all ofthe transducers may be positioned on the peripheral region 206 in someembodiments. Other circuit components may additionally or alternativelybe included on the peripheral region 206. Furthermore, in someembodiments, all integrated circuitry of the ultrasound transducer probemay be positioned beneath the ultrasonic transducers, which may minimizethe chip area required for the ultrasound transducer probe.

Ultrasound Transducer Probe Circuitry

The architecture of the ultrasound transducer probe circuitry mayinclude further features facilitating the use of the ultrasoundtransducer probe as a stand-alone probe or as a component of a largerultrasound device formed by tiling and interconnection of multipleinstances of the transducer probe. For example, the circuitry of thetransducer probe may include digitization circuitry (e.g.,analog-to-digital converters (ADCs)). Such digitization circuitry maydigitize signals from the ultrasonic transducers such that theultrasound transducer probe may communicate the ultrasound data to anexternal device in digital form (e.g., via a USB cable or otherinterface of the types described herein). Thus, aspects of the presentapplication provide digital ultrasound transducer probes. Examples ofsuitable digital circuitry are described further below and may include,for example, analog-to-digital converters (ADCs), multiplexers,re-quantizers, averaging circuits, and communication interfaces, amongothers.

Another feature of the ultrasound transducer probe circuitry which mayfacilitate the use of the ultrasound transducer probe as a stand-aloneprobe or as a component of a larger ultrasound device formed by tilingand interconnection of multiple instances of the transducer probe is theprogrammable nature of the circuitry. The use of programmable circuitrymay allow the ultrasound transducer probe to be programmed to worksuitably in combination with other such ultrasound transducer probes(e.g., when two or more ultrasound transducer probes are tiled to form alarger ultrasound transducer probe). Also, the use of programmablecircuitry may support various ultrasound imaging modes. In someembodiments, the programmable circuitry may include a programmablewaveform generator. Non-limiting examples of such waveform generators aswell as other circuitry of an ultrasound transducer probe are describedfurther below.

The control circuitry of an ultrasound transducer probe of the typesdescribed herein (e.g., integrated circuitry 306 of ultrasoundtransducer probe 300) may include any suitable circuitry forcontrolling, at least in part, transmission and/or receiving functionsof the plurality of ultrasonic transducers of the transducer probe(e.g., ultrasonic transducers 304). FIG. 7 illustrates a non-limitingexample of a suitable configuration for the circuitry of an ultrasoundtransducer probe.

The ultrasound transducer probe 700 includes one or more transducerarrangements (e.g., arrays) 702, a transmit (TX) control circuit 704, areceive (RX) circuit 706, a timing and control circuit 708, a signalconditioning/processing circuit 710, and/or a power management circuit718 receiving ground (GND) and voltage reference (V_(IN)) signals.Optionally, a HIFU controller (not shown) may be included if theultrasound transducer probe is to be used to provide HIFU. In theembodiment shown, all of the illustrated elements are formed on a singlesemiconductor die (or substrate or chip) 712, though not all embodimentsare limited in this respect. In addition, although the illustratedexample shows both a TX control circuit 704 and an RX circuit 706, inalternative embodiments only a TX control circuit or only an RX controlcircuit may be employed. For example, such embodiments may be employedin a circumstance in which the ultrasound transducer probe is operatedas a transmission-only device to transmit acoustic signals or areception-only device used to receive acoustic signals that have beentransmitted through or reflected by a subject being ultrasonicallyimaged, respectively.

The ultrasound transducer probe 700 further includes a serial outputport 714 which may represent an implementation of an interface of thetypes previously described herein (e.g., interface 308 a or 308 b).While only a single output port 714 is illustrated, it should beappreciated that multiple output ports may be provided, consistent withthe ultrasound transducer probe 700 having multiple interface types.

The ultrasound transducer probe 700 may also include a clock input port716 to receive and provide a clock signal CLK to the timing and controlcircuit 708.

It should be further appreciated from the components of ultrasoundtransducer probe 700 that a complete ultrasound system-on-a-chip may beprovided in accordance with some embodiments. Not all embodiments arelimited to such a configuration, however.

In some embodiments, the control circuitry of an ultrasound transducerprobe may be configured to reduce the amount of data to be sent from thetransducer probe to an external device. Reducing the amount of data mayfacilitate use of the ultrasound transducer probe for high endapplications, such as high end ultrasound imaging applications.According to some embodiments, the amount of data provided externallyfrom the ultrasound transducer probe may be reduced by including fewerreceive signal channels than the probe contains ultrasound elements,such that multiple ultrasound elements share a receive signal channel.Thus, the receive circuit 706 and signal conditioning/processing circuit710 may be shared among multiple ultrasound elements. A non-limitingexample is illustrated in FIG. 8.

As shown, the circuitry configuration 800 includes a plurality ofultrasound elements 802, which may be of the types previously describedherein or any other suitable type. For example, the ultrasound elements802 may each be like an ultrasound element 508 a, previously described.A respective transmit excitation module 804 may be provided for each ofthe ultrasound elements 802. However, multiple ultrasound elements 802share a single receive module 806. For example, the illustratedultrasound elements 802 may each be coupled to the receive module 806 bya respective switch 808. In this manner, the amount of receive circuitryimplemented on the ultrasound transducer probe may be reduced and theamount of data provided by the ultrasound transducer probe to anexternal device may be more readily reduced to an amount which can becommunicated serially.

In those embodiments in which multiple ultrasound elements 802 share asingle receive module 806, the number of ultrasound elements 802 sharingthe receive module 806 may be any suitable number to provide a desiredreduction in receive circuitry compared to providing a respectivereceive module for each ultrasound element. Referring to FIG. 5A andconsidering the ultrasound transducer probe 210 as a non-limitingexample, two receive circuits (e.g., two receive modules 806) may beprovided for each column of ultrasound elements 504, such that eightultrasound elements 504 may share a single receive circuit. However,this is a non-limiting example, as any two or more ultrasound elementsmay share a receive circuit in those embodiments in which multipleultrasound elements share a receive circuit.

The switches 808 may be operated in any suitable manner to providedesired receive functionality. For example, all the switches 808 may beopen, disconnecting the receive module 806 from the ultrasound elements802, when the ultrasound elements 802 are transmitting ultrasoundsignals. When the ultrasound elements 802 are receiving ultrasoundsignals, the switches 808 may be sequentially closed to read signals outof the ultrasound elements 802 sequentially, as a non-limiting example.

FIG. 9 illustrates a non-limiting example of the control circuitry of anultrasound transducer probe of the types described herein which may beused as a universal building block ultrasound transducer probe fortiling and interconnection with other such ultrasound transducer probes.Thus, the ultrasound transducer probe 900 represents a non-limitingdetailed implementation of the circuitry of ultrasound transducer probe700 of FIG. 7, and conforms to the configuration of FIG. 8 in thatmultiple ultrasound elements share a receive module.

The ultrasound transducer probe 900 includes a plurality of ultrasoundelements 901 which, for purposes of illustration, are described as beingarranged in columns. For example, the ultrasound elements 901 may bearranged in columns in the manner previously described in connectionwith ultrasound transducer probe 210 as shown in FIG. 5A. In thenon-limiting example of FIG. 9, each occurrence of “901” representseight ultrasound elements, such that each illustrated column includes 16ultrasound elements.

Certain circuitry of the ultrasound transducer probe 900 is associatedwith respective columns of the ultrasound elements 901 and thus isdescribed as being part of a column module, each of which is shown asbeing divided into two half-columns. Other circuitry is more generallyassociated with the plurality of ultrasound elements 901 rather than anyparticular column of ultrasound elements and thus may be consideredseparate from the column modules.

The ultrasound transducer probe 900 includes column modules 902 a, 902 b. . . 902 n, where n is the total number of columns of ultrasoundelements. As a non-limiting example, n may be 128, may be between 50 and150, any value within that range, or any other suitable value. Thecolumn modules 902 a . . . 902 n may each include a subset of theultrasound elements 901, one or more transmit circuitry modules 904 andone or more receive circuitry modules 906. In the non-limiting exampleshown, each column module 902 a . . . 902 n may include 16 ultrasoundelements 901, two receive circuitry modules 906 coupled to respectivegroups of eight ultrasound elements 901 (i.e., one receive circuitrymodule per 8 ultrasound elements), and 16 transmit circuitry modules 904coupled to respective ultrasound elements 901 (i.e., one transmitcircuitry module 904 per ultrasound element 901). The receive circuitrymodules 906 may be coupled to each ultrasound element 901 of arespective group of ultrasound elements 901 by a switch in the mannerpreviously illustrated in FIG. 8, or in any other suitable manner. Thetransmit circuitry modules 904 are connected to each other in adaisy-chain configuration as illustrated by the arrows 962, which mayrepresent a wired connection (e.g., a data line), and also connected tothe excitation parameter loader 914, described further below.

The ultrasound transducer probe may operate by loading transmitparameters defining a sequencing operation into the transmit circuitrymodules of the column circuitry. In some embodiments, the sequencinginformation may be pushed to each ultrasound element of the ultrasoundtransducer probe by pushing the sequencing information to the waveformgenerator associated with the ultrasound elements. The transmitparameters may be loaded in a daisy-chain configuration, being passedfrom one transmit circuitry module to the next, as indicated by thearrows 962. In some embodiments, the transmit parameters are loaded intothe transmit circuitry modules when the ultrasound transducer probe isoperating in a receive mode.

Control of the sequencing of transmit and/or receive functions performedby the ultrasound transducer probe 900 may be achieved with the sequenceprocessing unit (SPU) 912, which may be a microcontroller or othersuitable hardware. For example, the SPU 912 may provide a desiredsequence of transmission and/or reception events.

Various components of the ultrasound transducer probe 900 may operate inconjunction with the SPU 912. For instance, an excitation parameterloader 914 is included and loads suitable control parameters into thetransmit circuitry modules 904 in response to a control signal 958 fromthe SPU 912. A SPU memory 916 is also included to store the sequencingparameters for the SPU 912, including transmit and receive parametersand parameters for controlling other components (such as data interfacecomponents) of the ultrasound transducer probe. A program managementunit (PMU) 917 may handle program loading into the SPU 912, and may be adedicated piece of hardware. The PMU 917 and SPU 912 may communicatedata and address information with the SPU memory 916 via control lines954 and 952, respectively, with the help of a multiplexer 960. The PMU917 may also provide a reset signal 956 to the SPU 912.

The SPU 912 may run a stored program to configure and sequence theactions of the ultrasound transducer probe 900. Thus, the details of animaging mode of operation may be encoded into a reconfigurable storedprogram loaded into the SPU 912. As described previously, the PMU 917may control loading of the program into the SPU 912. The PMU 917 may bedirectly accessible from the external device (e.g., a host computer)over the external data links 930 and 932 connected to the interfacecircuits 926 and 928, respectively. When commanded by the host computer,the PMU 917 may hold the SPU 912 in reset and take direct control of theSPU memory 916. Program code from the host computer may then be writtendirectly into the SPU memory 916. After the program has beentransferred, the PMU 917 may return the SPU memory 916 to the SPU 912and release the SPU 912 from reset. The new program may then beginexecuting per the program's reset vector.

The SPU 912 may be loaded with a suitable program at any suitable times.In some embodiments, the SPU 912 may be loaded with a program atpower-on and reset of the ultrasound transducer probe 900. In someembodiments, the stored SPU program may also be replaced duringoperation of the ultrasound transducer probe 900 as the host computer orother external device changes imaging modes. Thus, the SPU 912 mayexhibit semi-autonomous operation. That is, The SPU 912 may operatewithout a constant stream of configuration data from the host computer,which may eliminate performance bottlenecks caused by latency andcongestion on the external data links.

Various benefits may be realized by operation of the SPU 912 in themanner described. For example, when multiple instances of the ultrasoundtransducer probe 900 are tiled and interconnected, each may run its ownunique copy of the SPU program. The programs may or may not be identicaldepending on what the host computer is trying to achieve. In thismanner, coordinated operation of the multiple instances of therepeatable ultrasound building block may be achieved. Cascaded or commonclocks and sync pulses may be used to coordinate execution betweenmultiple such ultrasound transducer probes, described further below inconnection with FIG. 14.

The operation of the SPU 912 as described may also provide flexibilityto the ultrasound transducer probe 900. For example, the ultrasoundtransducer probe is not restricted to the imaging modes encoded on thechip during the design phase. Additional imaging modes can be achievedsimply by changing the stored program for the SPU.

Moreover, verification of operation of the ultrasound transducer probe900 may be relatively simple. That is, accuracy of operation may beverified by ensuring the SPU 912 can communicate with any externalimaging hardware through the designated interfaces, without the need toverify the operation of many hardware state machines.

The timing of operation of the ultrasound transducer probe 900 may becontrolled in any suitable manner. In the example shown, the ultrasoundtransducer probe 900 includes a clock and reset control circuit 910 forcontrolling the clocking of the circuitry (e.g., the transmit andreceive circuitry modules). For example, the clock and reset controlcircuit 910 may receive an input clock 934 (e.g., from an externaloscillator), and provide a global clock 936 and/or a global reset signal938. An external clock 940 may also be provided as an output.

The ultrasound transducer probe 900 also includes a referencevoltage/current circuitry module 918 to monitor and provide referencevoltages/currents to the column circuitry. The reference voltage/currentcircuitry module 918 may take any suitable form.

The ultrasound transducer probe 900 also includes interface circuitryfor communicating electrical signals between the ultrasound transducerprobe and an external device (e.g., a tablet computer or other hostcomputer). The interface circuitry includes a first interface circuit926 and a second interface circuit 928, which may be any of the typespreviously described herein or any other suitable types of interfacecircuits. An external communication module 924 may facilitatecommunication between the ultrasound transducer probe 900 and anyexternal device, and may be coupled to the interface circuits 926 and928. The external communication module 924 may be hardware and may takeany suitable form.

The external communication module 924 may also be used in providing datafrom the receive circuitry modules 906 to an external device. As shownby the arrows, each of the receive circuitry modules 906 may beconfigured to provide data to the external communication module 924.Different operating modes for doing so are possible. In one mode, eachof the receive circuitry modules 906 may provide its data to theexternal communication module, i.e., data for each half-column may beseparately provided to the external communication module 924. In anothermode, data from the two half-columns forming a column may be provided tothe external communication module 924 using the adders 942. Inparticular, the data from the receive circuitry modules 906 of the twohalf-columns of a column may be combined by the adder 942 of that columnand then provided to the external communication module 924. Thus, theadders 942 may optionally be used, and in some embodiments may bebypassed as shown by the arrows.

A time gain control (TGC) circuit 922 and TGC RAM 920 may also beincluded in the ultrasound transducer probe 900 to provide TGCfunctionality. The TGC RAM 920 may store data of a TGC curve to beimplemented by the TGC circuit 922. The TGC circuit 922 may be coupledto the receive circuitry modules 906 to adjust them suitably to provideTGC functionality. For instance, a global gain setting 944 may beprovided to all the columns. The slave line 946 may be the slave of theSPU 912. The SPU may send the time gain control to the TGC circuit 922which may then send out the TGC information via the global gain setting944.

The TGC circuit 922 and the TGC RAM 920 may exchange data 946 andaddresses 948 of the appropriate ultrasound elements 901 may be providedby the TGC circuit 922 to the TGC RAM 920. The TGC RAM 920 may alsoreceive data from the external communication module 924 via line 950.

The transmit circuitry modules and receive circuitry modules of FIGS. 8and 9 may take any suitable form and may include programmable circuitryin some embodiments. Non-limiting examples of transmit and receivecircuitry modules are illustrated in FIG. 10.

FIG. 10 illustrates a single half column of an ultrasound transducerprobe which may represent an embodiment of a half column of theultrasound transducer probe 900. As shown, the half column 1000 includesa plurality (eight in this example) of ultrasound elements 1002. Eachultrasound element 1002 is coupled to a respective transmit excitationmodule including a waveform generator 1008 and a pulser 1010. Theultrasound elements 1002 are switchably coupled to a single receivecircuitry module via switches 1014. In some embodiments, each ultrasoundelement may be connected to its own receive circuitry module, ratherthan having multiple ultrasound elements share a receive circuitrymodule.

The waveform generator 1008 may be a programmable waveform generator. Insome embodiments, the waveform generator 1008 may be configured toproduce various kinds of waveforms, including continuous waves,impulses, coded excitations, and chirp waveforms. A non-limiting exampleof a suitable waveform generator is described further below inconnection with FIG. 11. As illustrated, the waveform generators 1008may be coupled in a daisy-chain configuration, such that the transmitparameters (labeled as “TX Configuration Parameters”) controllingoperation of the waveform generators may be passed from one waveformgenerator to the next.

The pulser 1010 may be any suitable type of pulser, non-limitingexamples of which are described further below, for example in connectionwith FIG. 12. In some embodiments, the pulser 1010 may be a tri-levelpulser. The pulser may be bipolar, configured to drive positive andnegative voltages, although unipolar pulsers may be used in someembodiments.

In the example of FIG. 10, a transimpedance amplifier (TIA) 1004 may becoupled to two ultrasound elements 1002 via transmit/receive switches1012, which may control whether the half-column is operating in atransmit mode or a receive mode. The TIA may be the implemented form ofan LNA in some embodiments because current may be the quantity ofinterest in the receive circuitry module. For example, in thoseembodiments in which the ultrasound element 1002 is made up of one ormore CMUTs or CUTs, the velocity of the CMUT or CUT membrane may beproportional to the magnitude of current provided from the CMUT or CUT.

As illustrated in FIG. 10, the ultrasound elements 1002 may be coupledto the receive circuitry module by switches 1014. In the illustratedembodiment, four switches 1014 are provided for the eight ultrasoundelements 1002. However, in some embodiments each ultrasound element 1002may be coupled via its own switch to the receive circuitry module. Anysuitable number of ultrasound elements 1002 may share a switch 1014. Inthis manner, the ultrasound elements 1002 may be configured into varioussub-arrays.

When the ultrasound transducer probe operates in a transmit mode, theswitches 1014 may all be opened, disconnecting the ultrasound elements1002 from the receive circuitry module. When the ultrasound elements1002 operate in a receive mode, the switches 1014 may be closed in anysuitable sequence to connect the ultrasound elements 1002 to the receivecircuitry module and thus read a signal out from one or more of theultrasound elements 1002. It should be appreciated that switches 1014provide a degree of configurability in determining whether the outputsfrom the ultrasound elements 1002 are provided by two ultrasoundelements at a time, eight ultrasound elements at a time, or some numberin between.

The switches 1014 couple the ultrasound elements 1002 to a multiplexingor summing circuit 1016. The multiplexing or summing circuit 1016 maycouple an ultrasound element 1002 to a variable gain amplifier (VGA)1018. In some embodiments, the VGA 1018 may include a filter, such as asecond order low-pass filter. The output of the VGA 1018 may be coupledto an analog-to-digital converter (ADC) 1020 to digitize the outputsignals of the ultrasound elements 1002.

The TIAs 1004 and VGA 1018 may be configured in combination to providetarget noise characteristics in view of the configurable nature of theillustrated circuit. That is, use of the VGA 1018 in combination withthe TIAs 1004 may account for the fact that the switches 1014 may beoperated to alter whether a single ultrasound element 1002 is providingits output at any given time or whether all eight ultrasound elements1002 are providing their outputs simultaneously. The illustratedconfiguration of TIAs 1004 and VGA 1018 may also reduce the amount ofchip area compared to if a single TIA or VGA was provided for eachultrasound element. In some embodiments, the TIAs 1004 (or, moregenerally, the LNAs) and/or VGA 1018 may be powered down when not used(e.g., during transmit modes). By powering down the TIAs 1004 and/orVGAs 1018 during idle and/or non-transmit modes, overall powerconsumption of the device may be reduced.

The VGA 1018 may function to adjust the gain of the signals receivedfrom the ultrasound elements 1002 to provide a substantially constantpower level over the duration of the receive time window. For a givenexcitation event, the signals received by the ultrasound elements 1002may generally decrease in magnitude as time progresses. If the magnitudebecomes too low, the signal may fall below the threshold of the ADC1020. By providing a time varying gain, the VGA 1018 may prevent suchbehavior, thus allowing for ultrasound analysis of a wider region withina subject. The time varying gain profile implemented by the VGA 1018 maybe provided by, for example, the TGC circuit 922 of FIG. 9.

Additional circuitry of the receive circuitry module 1006 may include alow pass filter (LPF) 1022, a multiplexer 1024, a maximum valuedetection circuit 1026, an output buffer 1028 and a re-quantizer 1030.Signals received by the receive circuitry module from one or more of theultrasound elements 1002 may be digitized by the ADC 1020, then filteredby the LPF 1022, and re-quantized by the re-quantizer 1030. The LPF 1022may be any suitable low pass filter for filtering a desired frequencyrange. In some embodiments, the LPF 1022 may be a decimating filter, andin some embodiments a ½ band decimating filter. Other types of low passfilters may alternatively be used.

The re-quantizer 1030 may reduce the amount of data to be sentexternally from the ultrasound transducer probe. Any suitablere-quantizer for performing this function may be used. The re-quantizermay operate to discard data bits not of interest or not needed toproduce ultrasound data of a desired quality. As a non-limiting exampleof the operation, the re-quantizer 1030 may determine a maximum datavalue from a set of received data. A count of the number of shifts(e.g., to the left) within the data set to get to a position at whichthe two most significant bits differ from those of the maximum datavalue may then be made. This determined count may be provided to an enduser of the ultrasound transducer probe. Then, as the ultrasound data issent externally from the ultrasound transducer probe, all the datavalues may be shifted (e.g., to the left) by the determined count andthe upper N rounded bits may be sent. N represents an integer and may beset at a desired level (e.g., the upper five bits, upper seven bits,upper eight bits, or other suitable value) to achieve sufficient datareduction. It should be appreciated that this process of re-quantizationis a lossy process, but that by suitable selection of N the ultrasounddata sent externally from the ultrasound transducer probe may be ofsufficiently high quality to enable desired applications (e.g., imagingapplications) of the ultrasound transducer probe while providing datareduction.

The output 1032 of the receive circuitry module may represent the datafrom the ultrasound elements 1002 and may be provided, for example, tothe external communication module 924 of FIG. 9. A parallel businterface 1034 may also be provided and may, for example, communicatewith the TGC circuit 922 of the ultrasound transducer probe in themanner previously described in connection with FIG. 9.

The circuitry of FIG. 10 may sample the signals received by theultrasound element 1002 at any suitable frequency. According to anembodiment, quadrature sampling may be used, which may reduce the numberof samples taken and allow more efficient operation.

The receive circuitry positioned downstream of the ADC 1020 may also beconfigured to perform cancellation of signals. For example, two pulse orthree pulse cancellation techniques may be implemented. Other modesimplementing techniques such as addition or averaging of signals,subtraction of signals, or bit shifting techniques may be used tofacilitate cancellation of signals. Such cancellation may, for example,facilitate measurement of non-linear responses and scatterer velocities.

FIG. 11 illustrates a non-limiting detailed example of the waveformgenerator 1008 which, as described, may be programmable in someembodiments and which may be configured to produce different kinds ofwaveforms, including impulses, continuous waves, chirp waveforms, andcoded excitations. As shown, the waveform generator 1008 may includeregisters 1102, 1104, and 1106. Register 1102 may store one or morevalues relating to a desired rate of change of the frequency of thegenerated waveform, i.e., the chirp rate, r. Register 1104 may store oneor more values relating to an initial frequency of the waveform, f₀.Register 1106 may store one or more values relating to an initial phaseof the waveform, θ₀. Thus, the waveform generator 1008 may beprogrammable, allowing for three degrees of freedom by allowing theregisters 1102, 1104, and 1106 to be set. Additional degrees of freedommay be provided as described below. Summation circuits 1108 and 1110 maybe provided to suitably sum the values from the registers 1102, 1104,and 1106 as shown. The combination of the summation block 1108 andregister 1104 forms an accumulator, as does the combination of thesummation block 1110 and register 1106. The values from registers 1104and 1106 may be loaded into the respective summation blocks prior tooperation. In some embodiments, the accumulators may also be configuredas decrementers (e.g., to provide a chirp up and a chirp down). In someembodiments, the accumulated values may be reset with a reset operation,such as a bit shift or modulo operation.

The waveform generator 1008 further comprises comparison circuits 1112and 1114. The comparison circuit 1112 compares the phase of thegenerated waveform to ±V_(T). Comparison circuit 1114 compares theinverse phase of the generated waveform (θ+180°) to ±V_(T). The outputsof comparison circuits 1112 and 1114 are provided to multiplexers 1120and 1122, which provide output signals V0 and V1 to the pulser 1010. Theoutput signals V0 and V1 may be binary signals. V_(T) represents thevalue the sine wave, as represented by the phase, needs to achievebefore triggering the pulser 1010 to transition. V_(T) may be tunable,thus representing an additional degree of freedom.

The waveform generator 1008 includes multiple components providing theability to generate coded excitations (e.g., binary coded excitations).As shown, a multiplexer 1128, multiplexer 1132 and AND gate 1130 allreceive an indication of whether a coded excitation is to be generated.The multiplexers 1128 and 1132 receive the indication as a controlsignal and each have one input configured to receive a zero. The ANDgate 1130 receives the indication as an input.

A flip bit circuit is also provided, including a flip bit register 1124configured to store a flip bit that flips the output signals V0 and V1,which is provided to an input of a XOR gate 1126 that also receives theoutput of the multiplexer 1128. Thus, the flip bit, which may be astatic bit, may provide for inversion of the waveform generatorwaveform. AND gate 1136 is also provided and has an inverting input asshown. The output of summation circuit 1110 is provided to one input ofthe AND gate 1136 and is also delayed by delay element 1134 and thenprovided to the inverting input of the AND gate 1136, the output ofwhich is provided as an input to the AND gate 1130.

The illustrated configuration allows for the turning on and off ofvarious components depending on whether coded excitation is to beperformed. In operation, the registers 1102, 1104, and 1106 are loaded.The waveform generator 1008 receives a clock signal 1116, for examplefrom a clock generation circuit (not shown in FIG. 11), and a transmitenable signal 1118, for example from a master timer (not shown in FIG.11). The transmit enable signal 1118 may be a delayed transmit signalproduced by a delay block 1138. The delay block 1138 may provide acoarse and/or fine delay, and thus may provide an additional degree offreedom. In some embodiments, the start time of a waveform and thewaveform duration may be set, providing two degrees of freedom.

If coded excitation is to be performed, values from register 1102 may befed through the multiplexer 1128 to the XOR gate 1126. Thus, theregister 1102 may serve a dual purpose in providing values to set achirp rate when a chirp is generated or to provide values to generate abinary coded excitation. When a coded excitation is to be generated, theoutput of multiplexer 1132 is the static value zero. The illustratedindication of the 2^(nd) most significant bit (MSB) provided to theinput of AND gate 1136 indicates the frequency of coding to beperformed. Any number of significant bits may be provided from theoutput of summation circuit 1110 to provide a desired frequency ofcoding, as the 2^(nd) MSB is an example.

Whether or not coded excitation is performed, the comparison circuits1112 and 1114 may perform the described comparisons to generate thevalues of V0 and V1 which may then be provided to the pulser 1010.

Thus, it should be appreciated that the waveform generator 1008 is aprogrammable waveform generator which may be programmed to producedifferent kinds of waveforms by setting the registers 1102, 1104, and1106 and controlling whether coded excitation is to be provided or not.In this manner, flexibility and versatility of the ultrasound transducerprobe may be provided. High end imaging modalities may be implemented,taking advantage of the ability to generate continuous wave excitations,impulse excitations, coded excitations, and chirp excitations. Moreover,different kinds of waveforms may be generated for different ultrasoundelements of an ultrasound transducer probe, or at different times ofoperation. In some embodiments, the same kind of waveform may begenerated by two different waveform generators of the ultrasoundtransducer probe, but with different parameterizations, for exampledifferent amplitudes and/or delays (or any other characteristic of awaveform).

The registers of waveform generator 1008 may have any suitable sizes, asthe exact sizes are not limiting of the various aspects of the presentapplication. In some embodiments, the register sizes may be betweenapproximately eight and approximately 32 bits, although other sizes mayalternatively be implemented.

In some embodiments, Hadamard coding may be implemented in connectionwith waveform generation. Such coding may be used, for example, tofacilitate apodization. The ultrasound transducer probe may includecircuitry to implement the Hadamard coding.

FIG. 12 illustrates a non-limiting example of the pulser 1010. Aspreviously described, in some embodiments the pulser 1010 may be atri-level pulser. The pulser 1010 may receive five input signals,including Vhigh, Vlow, Vm, V0, and V1. As previously described, V0 andV1 may be provided by the waveform generator (e.g., waveform generator1008), and may be binary signals. Vhigh, Vlow, and Vm may be provided bya voltage source 1202, for example by the voltage/current circuitrymodule 918. The pulser may provide an output signal 1204, which may be abipolar signal (i.e., having positive and negative voltages) or aunipolar signal in some embodiments. FIG. 12 includes a tableillustrating the output value of output signal 1204 as a function of theinput values V0 and V1. The indicated output value “High Z” when V0 andV1 both have a value of 1 refers to disconnecting the pulser 1010 fromthe ultrasound elements (e.g., open-circuiting the connection betweenthe pulser and the ultrasound element).

The pulser 1010 may provide any suitable output voltages for aparticular application. In some embodiments, the pulser may outputvoltages between approximately 5 V and approximately 20 V (e.g., 7.5 V),between approximately 20 V and approximately 120 V, any range or valuewithin such ranges, or any other voltage.

FIG. 13 illustrates a more detailed example of the configuration of asubcircuit including a pulser, an ultrasound element, and an amplifier(e.g., a LNA, such as a TIA) of an ultrasound transducer probe accordingto an embodiment of the present application, as may be used in theconfiguration of FIG. 10. The subcircuit 1300 includes the pulser 1010,ultrasound element 1002, and amplifier 1305. The pulser 1010 receivesinputs V0 and V1 as previously described, as well as reference voltagesVcc and Vss1. The output of the pulser 1010 may be biased by a signalVbias1.

The ultrasound element 1002 includes a first electrode 1302 facing atarget subject (e.g., a medical patient). The first electrode 1302 maybe configured to receive a voltage Vbias3. The ultrasound element 1002further includes a second electrode 1304 that is distally positionedfrom the target subject. The second electrode 1304 may be coupled to theoutput of the pulser 1010 by the switch S1. The second electrode 1304may also be coupled to the input of the amplifier 1305 by a switch S2.The input of the amplifier 1305 may also be biased by a bias signalVbias2. The amplifier 1305 may receive reference voltages Vdd and Vss2.

The voltages illustrated in FIG. 13 may take various values depending onthe manner of operation. According to some embodiments, Vbias1 andVbias2 may be substantially equal, and have a value betweenapproximately 30 V and approximately 90 V (e.g., 75 V). Vcc may be equalto Vbias1 plus some positive offset (e.g., Vcc=Vbias1+18 V). Vss1 may beequal to Vbias1 minus the offset (e.g., Vss=Vbias1−18 V). Vdd may beequal to Vbias1 plus a smaller positive offset than used for Vcc (e.g.,Vdd=Vbias1+5 V), while Vss2 may be equal to Vbias1 minus this smalleroffset (e.g., Vss2=Vbias1−5 V). Vbias3 may be grounded in thisconfiguration, which may minimize the risk of electrically shocking thesubject. Voltages other than those described above may be implemented.

According to some embodiments, Vbias1 and Vbias2 may be electricallygrounded (e.g., set to 0 V). Vbias3 may bias the first electrode 1302,for example at a value between −30 V and −90 V (e.g., −75 V). Vcc andVss1 may be set to approximately 18 V and −18 V, respectively, and Vddand Vss2 may be set to approximately 5 V and −5 V, respectively. WhenVbias3 is not grounded, the electrode 1402 may be covered with aninsulating material to reduce the risk of shock. Voltages other thanthose listed may be implemented.

The generation of clock signals within an ultrasound transducer probe ofthe types described herein may be performed in a manner whichfacilitates tiling and coordinated operation of multiple instances ofthe ultrasound transducer probe. When ultrasound transducer probes aretiled and interconnected for coordinated operation, one of theultrasound transducer probes may serve as a controller or master and theother probe(s) may serve as controlled probes. For example, consideringFIG. 2C as an example, the ultrasound transducer probe 200 on the leftside of the figure may serve as a master and the ultrasound transducerprobe 200 on the right side of the figure may be controlled, at leastwith respect to clocking.

FIG. 14 illustrates an example of a manner of generating clock signalswithin an ultrasound transducer probe, and is generic to whether theprobe is operating as a master probe or a controlled probe. As shown,the clock generation circuit 1403 may receive an external clock signal1404 produced by an oscillator 1401 and phase-locked loop (PLL) 1402located external to the ultrasound transducer probe. The clock signal1404 may be a high frequency clock signal (e.g., between approximately1.5 GHz and approximately 6 GHz, approximately 2.5 GHz, approximately 5GHz or any other suitable frequency).

In the illustrated embodiment, the clock generation circuit 1403 maydivide the clock signal 1404 by a desired amount and distribute thedivided signal(s). For example, as shown, the clock generation circuit1403 may include a SerDES module 1406, the output of which may beprovided to a first division circuit 1408. The output of divisioncircuit 1408 may represent a word clock in some embodiments, such as aninternal USB word clock to be used internally on the ultrasoundtransducer probe. The clock signal 1404 may also be provided to a seconddivision circuit 1410, the output of which may be provided to amultiplexer 1412. The multiplexer 1412 also receives an external digitalclock signal 1424, which may represent a digital clock signal providedby another ultrasound transducer probe, for example when the illustratedprobe is operating as a controlled probe.

The output of multiplexer 1412 may be used to produce both an internaldigital clock signal 1420 to be used within the ultrasound probe and anexternal digital clock signal 1426 representing the output of buffer1414. The external digital clock signal 1426 may be provided to anothercontrolled ultrasound transducer probe as its external digital clocksignal 1424.

The output of multiplexer 1412 may also be provided to a third divisioncircuit 1427, the output of which may be provided to a multiplexer 1416.The multiplexer 1416 also receives an external ADC clock signal 1428which may be provided by another ultrasound transducer probe when theillustrated ultrasound transducer probe is part of a tiled set ofultrasound transducer probes and is operated as a controlled probewithin the set.

The output of multiplexer 1416 may serve as an internal ADC clock 1422for clocking ADCs of the ultrasound transducer probe. The output of themultiplexer 1416 may also be sent to a buffer 1418 to produce anexternal ADC clock signal 1430 to be sent to other controlled ultrasoundtransducer probes.

Thus, it should be appreciated that the configuration of FIG. 14 allowsfor clocking signals to be sent from one ultrasound transducer probe toanother ultrasound transducer probe in a manner that allows forcoordinated operation. An alternative manner for providing suchcoordinate operation is to have a respective PLL on each ultrasoundtransducer probe. A lower frequency clock than clock 1404 may beprovided to the PLLs of the ultrasound transducer probes and eachtransducer probe may derive its own clock signals from the distributedlower frequency clock.

Configurability of ultrasound transducer probes according to aspects ofthe present application may also be provided through configuration ofthe circuitry for offloading data from the ultrasound transducer probeto an external device. FIG. 15 illustrates a non-limiting exampleutilizing a mesh configuration.

The mesh 1500 includes receiver channels 1502 and external links 1504a-1504 d. The illustrated embodiment includes 256 receiver channels,which may be utilized with an ultrasound transducer probe including16×128 ultrasound elements with the columns of ultrasound elements beingconfigured such that there are two receiver channels per column, forexample as described in connection with FIG. 9. The external links 1504a-1504 d may correspond to the previously described interfaces (e.g.,interfaces 208 a and 208 b). In the illustrated example, the externallinks 1504 b-1504 d may represent higher speed links, and the externallink 1504 a may be used as either a higher speed link or a lower speedlink (e.g., a USB link).

The mesh 1500 is configurable to shift data horizontally and/ordiagonally to send the data external to the ultrasound transducer probevia one or more of the external links 1504 a-1504 d. As shown, thereceiver channels 1502 are connected to nodes 1512 by signal paths 1508,which may include any number of signal lines (e.g., four as anon-limiting example). Data can be shifted horizontally from a node 1512to an external link 1504 a-1504 d by signal paths 1506 and/or shifteddiagonally to another node 1512 by signal paths 1510. The signal paths1506 and 1510 may include any suitable number of lines. In someembodiments, the signal paths 1506 include four lines and the signalpaths 1510 include two lines. Further detail is illustrated in FIG. 16.

Two receiver channels 1502 are shown in FIG. 16 as being connected torespective nodes 1512. Data 1602 may be provided to shift registers 1604which output parallel data to sampling RAM 1606, which in turn providesthe data to shift registers 1608. The shift registers 1604 and 1608 mayshift the data in the direction indicated by the arrows in FIG. 16. Thesignal paths 1508 may include four signal lines 1610 a-1610 d, and thedata may be output from the shift registers 1608 to one or more of thesignal lines 1610 a-1610 d to go to the nodes 1512. As previouslydescribed in connection with FIG. 9, in one mode of operation the datafrom two half-columns (e.g., the two illustrated receiver channels 1502in FIG. 16) may be summed via adders 942. In such operation, the datamay be provided to only one of the two nodes 1512 shown in FIG. 16.

The signal paths 1510 interconnecting the nodes 1512 to allow diagonaldata shifting may include any suitable number of lines. In theembodiment illustrated, two lines 1612 a and 1612 b make up the signalpaths 1510 but alternatives are possible.

The nodes 1512, which may be shift registers in some embodiments, may becontrollable to offer flexible operation depending on a desiredoperating mode. An example is shown in FIG. 17. The data from thereceiver channels may be injected to the node at an input “INJECT.” Amode control signal 1702 may be provided to a MODE input. The nodes 1512may be controlled by, for example, the external communication module 924of FIG. 9, which may provide the mode control signal 1702. The value ofthe mode control signal 1702 may dictate whether data is shiftedhorizontally through the node 1512 via the H IN and H OUT ports orwhether the data is shifted diagonally via the D IN and D OUT ports.Whether horizontal and/or diagonal shifting is performed may depend onhow many of the external links 1504 a-1504 d are to be used inoperation.

For example, if all four external links 1504 a-1504 d are to be used(e.g., when the amount of data sent externally and frame rate are to bemaximized in some embodiments), diagonal shifting and the associateddata aggregation may be omitted. The data may be provided by thereceiver channels to the respective nodes 1512 and shifted horizontallyalong lines 1506 to the respective external links 1504 a-1504 d.

By contrast, if only a single external link 1504 a is to be utilized,whether it be a higher speed link or a lower speed link, data from thereceiver channels coupled to nodes 1512 not on the horizontal signalpath 1506 connected to external link 1504 a may be shifted by the nodes1512 diagonally to the horizontal signal path 1506 connected to externallink 1504 a. The data may then be shifted horizontally to the externallink 1504 a.

Two non-limiting examples of modes of operation of the mesh 1500 areshown in FIGS. 18A and 18B. The method 1800 of FIG. 18A illustrates amanner of operation using only one or two of the external links 1504a-1504 d, rather than all four. At stage 1802, data is injected from thereceiver channels 1502 into the mesh network. At stage 1804, the data isdiagonally shifted and aggregated by the nodes 1512. At stage 1806 adetermination is made whether the diagonal shifting is complete, orwhether diagonal shifting needs to be repeated to shift the data to thehorizontal signal paths connected to the external links being used. Ifthe diagonal shifting is not complete, the method returns to stage 1804.If the diagonal shifting is complete, the method proceeds to stage 1808to horizontally shift the data down the signal paths 1506 connected tothe external links being utilized.

At stage 1810 a determination is made whether the data has beenoffloaded from the ultrasound transducer probe. If not, the methodreturns to stage 1808 for further horizontal shifting. If yes, themethod moves to stage 1812 at which a determination is made whetherthere is a next frame to be processed. If yes, the method returns tostage 1802. If not, the method is completed.

The method 1850 of FIG. 18B may be implemented when all four externallinks 1504 a-1504 d are used. In such an embodiment, no diagonalshifting from the nodes 1512 may need to be performed. The method 1850begins at stage 1852 by injecting data from the receiver channels intothe mesh network. At stage 1854 the data is horizontally shifted by thenodes 1512. At stage 1856 a determination is made whether the data hasbeen offloaded from the ultrasound transducer probe. If not, the methodreturns to stage 1854. If so, the method proceeds to stage 1858 todetermine whether a next frame needs to be processed. If so, the methodreturns to stage 1852. If not, the method is completed.

Thus, the circuitry configuration for offloading data from an ultrasoundtransducer probe may also be configurable. The described configurabilitymay facilitate the use of the ultrasound transducer probe in a varietyof applications with different requirements such as data frame rates,amount of data, and speed of operation.

Thus, it should be appreciated from the foregoing discussion thatseveral aspects of the architecture of an ultrasound transducer probeaccording to embodiments of the present application, including probegeometry and circuitry positioning and programmability, may facilitateuse of an ultrasound transducer probe as either a standalone ultrasoundtransducer probe or as a repeatable unit to tile and interconnect withother such ultrasound transducer probes in a larger ultrasound device.Further features of the architecture may facilitate operation of theultrasound transducer probe(s) for particular applications, as nowdescribed.

High Voltage Circuitry

Aspects of the present application provide for integration of ultrasonictransducers with circuitry on a single substrate, such as a CMOSsubstrate or chip. The ultrasonic transducers may be used for ultrasoundimaging applications, HIFU, or both. In some embodiments, the ultrasonictransducers may operate at voltages higher than those conventionallyused for CMOS integrated circuitry, e.g., higher than voltages typicallysupported by deep and ultra-deep submicron CMOS circuitry. For example,such ultrasonic transducers may operate at voltages between 20 V and 120V, between 30 V and 80 V, between 40 V and 60 V, at any voltage withinthose ranges, or at any other suitable voltages, depending on theapplication. HIFU applications typically utilize higher voltages thanultrasound imaging applications. In some embodiments, submicron nodesmay refer to nodes that are smaller than approximately 1 micron. In someembodiments, deep submicron nodes may refer to nodes that are smallerthan approximately 0.3 microns. In some embodiments, ultra-deepsubmicron nodes may refer to nodes that are smaller than approximately0.1 micron.

Thus, in those embodiments in which ultrasonic transducers areintegrated with circuitry on a single substrate it may be desirable forsuch circuitry to be configured to sustain or withstand voltages in theranges listed above, for example by supporting those higher-than-typicalvoltages at deep submicron nodes of the integrated circuitry. Thecircuitry may be configured in some embodiments to account for typicallimits on the operating voltage of NMOS and PMOS devices in CMOScircuits arising due to: (1) gate oxide breakdown, and (2) source anddrain (diffusion) breakdown.

To increase the diffusion breakdown limit to enable operation at highervoltages, suitable doping of the source and drain regions of any fieldeffect transistor (FET) may be implemented. For example, lowering dopinglevels in the source and drain regions may increase the diffusionbreakdown voltage. In some embodiments doping levels below 10¹⁷dopants/cm³ may be implemented.

With respect to gate oxide breakdown, which can arise as eithergate-to-drain breakdown or gate-to-source breakdown, the maximumelectric field applied across those points should be reduced. Thestandard gate-to-drain interface is a Lightly Doped Drain (LDD). The LDDmay, for example, be doped to reduce the electric field but may beminimized in size to keep device length large enough to maintain gatecontrol.

Aspects of the present application provide CMOS circuit designs suitablefor use in ultrasound transducer probes of the types described hereinand which exhibit breakdown voltages greater than those of conventionalCMOS circuits. According to an aspect of the present application, masklogic operations and device layout are selected to provide suitable CMOScircuits for sustaining high voltages at deep submicron nodes.

CMOS circuitry may, for example, be turned into high-voltage CMOScircuitry by changing the diffusion scheme. For example, a mask-alignedsource and drain using N-type well and P-type well regions may beemployed. For NMOS implementations, the diffusion may be changed to anN-type well source/drain configuration with P-type substrate. For PMOSimplementations, the diffusion may be changed to a P-type wellsource/drain configuration with N-type well and deep N-type wellfeatures. The sources and drains may be defined by Shallow TrenchIsolation (STI). Alternatively, to sustain even larger voltages, thesource and drain regions may be defined by gap space and thermaldiffusion.

Examples of CMOS circuit layouts and associated structures that may beused to implement high-voltage CMOS circuits according to the variousembodiments set forth herein are shown in FIGS. 19-28B. Specifically,FIGS. 19-22 illustrate examples of MOS transistor configurations whichmay sustain high voltages. FIGS. 23-28B illustrate examples of circuitswhich may utilize such transistors and be employed in ultrasoundtransducer probes of the types described herein.

FIG. 19 shows an example of a high voltage NMOS transistor and PMOStransistor layout that may be used in some embodiments to provide highvoltages at deep submicron nodes. The illustrated example includes anepitaxial wafer formed of a P-type substrate 1902 with a P+ doped region1904, on which the transistors may be formed. The substrate 1902 mayhave a low doping (e.g., on the order of 10¹⁵ dopants/cm³) while the P+doped region 1904 may have a higher doping, for example on the order of10¹⁹ dopants/cm³. Although an epitaxial wafer is shown, it should beappreciated that high voltage NMOS and PMOS transistors may be formed onbulk wafers according to aspects of the present application, and thusthe illustration of an epitaxial wafer is not limiting. For example, thedoped region 1904 may be excluded in some embodiments.

The NMOS transistor 1906 includes N+ source and drain regions 1908 and1910, respectively. A source contact 1912 contacts the source region1908 and a drain contact 1914 contacts the drain region 1910. An N+ gate1916 is also included. The source region 1908 is formed in a P-type well(designated “PW”) 1918 which has a P+ contact region 1920 serving as abody contact for the transistor. The drain region 1910 is formed in anN-type well (designated “NW”) 1922. STI region 1924 is also included inthe N-type well 1922.

Various features of the illustrated transistor 1906 may contribute tothe ability to sustain high voltages. The configuration of the N-typewell 1922 and the P-type substrate 1902 may contribute to the transistor1906 having a large junction breakdown voltage. The N-type well 1922 andthe P-type well 1918 may be lightly doped, and thus the region under thegate 1916 may be a LDD, thereby reducing the electric field between thegate 1916 and the source region 1908 and drain region 1910.

The PMOS transistor 1926 may also be configured to sustain highvoltages. As shown, the PMOS transistor 1926 includes P+ source anddrain regions 1928 and 1930, respectively. A source contact 1932contacts the source region 1928 and a drain contact 1934 contacts thedrain region 1930. A P+ doped gate 1936 is also included.

The source region 1928 is formed in an N-type well 1938 which includesan N+ contact region 1940 serving as a body contact for the transistor.The drain region 1930 is formed in a P-type well 1942, in which is alsoformed STI region 1944. An N-type well 1946 with a N+ contact region1948 serving as a body contact for the transistor, as well as a deepN-type well (designated “DNW”) 1950, are also included as shown. Thedeep N-type well 1950 provides isolation from the substrate 1902. A deepwell may have a depth between approximately 1 micron and 8 microns.

The configuration of P-type well 1942 and N-type well 1938 contribute tothe transistor 1926 being able to support high voltages withoutexperiencing junction breakdown. The N-type well 1938 and the P-typewell 1942 may be lightly doped, and thus the region under the gate 1936may be a LDD, thereby reducing the electric field between the gate 1936and the source region 1928 and drain region 1930.

FIG. 20 shows an alternative configuration for an NMOS transistor andPMOS transistor, both of which can support high voltages. Compared tothe configuration of NMOS transistor 1906, the NMOS transistor 2002includes a P-type well 2004 and N-type well 2006 which do not touch. TheP-type well 2004 may be a thermally diffused well, and likewise theN-type well 2006 may be a thermally diffused well.

The spacing indicated by reference number 2010 represents an example ofa mask defining the N+ doping implant region for the transistor 2002. Itshould be appreciated that only part of the gate 2008 is doped N+.

The PMOS transistor 2012 differs from PMOS transistor 1926 in that theN-type well 2014 and P-type well 2016 do not touch each other as do theN-type well 1938 and P-type well 1942. Thus, a portion 2020 of theP-type substrate is disposed between the N-type well 2014 and the P-typewell 2016. The N-type well 2014 may be thermally diffused. Likewise, theP-type well 2016 may be thermally diffused.

The spacing indicated by reference 2022 represents an example of a maskdefining the P+ doping implant region of the transistor 2012. It shouldbe appreciated that only part of the gate 2018 is doped P+.

FIG. 21 shows an example of a high voltage NMOS and PMOS bidirectionalor cascoding layout that may be used in some embodiments as part of anultrasound transducer probe. The NMOS transistor 2102 includes an N-typewell 2104 in which is formed STI region 2106 in addition to the sourceregion 1908. The N-type well 2104 and N-type well 1922 do not touch, butrather are separated by P-type well 2108. The N-type well 2104represents a well for the source region 1908 and also a source gateextension. In this embodiment, the N-type well 1922 functions as a wellfor the drain region 1910 and also as a gate extension. A body contactfor the NMOS transistor 2102 is not explicitly shown but may be includedand may be formed, for example, by a P-type well with a P+ diffusionregion.

The PMOS transistor 2110 includes an N-type well 2114 with a N+ contactregion 2112 adjacent a P-type well 2116 in which is formed the sourceregion 1928 and STI region 2118. The N+ contact region 2112 serves as abody contact for the transistor. An N-type well 2020 separates P-typewell 2116 from P-type well 1942. The P-type well 2116 represents a wellfor the source region 1928 and also a gate extension. P-type well 1942operates as a well for the drain region 1930 and also as a gateextension.

The PMOS transistor 2110 also includes an N-type well 2120 and N+contact region 2122 serving as a body contact for the transistor.

FIG. 22 shows an example of an alternative high voltage NMOS and PMOSbidirectional or cascoding layout that may be used in some embodiments,and which may sustain higher voltages than those applicable to thelayout of FIG. 21. The NMOS transistor 2202 includes N-type wells 2208and 2210. An N+ source region 2204 is formed in the N-type well 2208. AnN+ drain region 2206 is formed in the N-type well 2210. The N-type wells2208 and 2210 are separated by a P-type well 2214 and by the P-typesubstrate 1902. The P-type well 2214 is optional and may increase thethreshold voltage at which the transistor 2202 breaks down. The N-typewells 2208 and 2210 may be thermally diffused.

The pattern illustrated by reference 2216 represents an example of amask pattern for the N+ implant region. As shown, only part of the gate2212 is doped N+.

A body contact for the NMOS transistor 2202 is not explicitly shown butmay be included and may be formed, for example, by a P-type well with aP+ diffusion region.

The PMOS transistor 2218 includes a deep N-type well 2220 formed in theP-type substrate 1902. N-type wells 2222, 2250 and 2238 may be formed inthe deep N-type well 2220. An N+ contact region 2224 serving as a bodycontact for the transistor may be formed in the N-type well 2222.Similarly, an N+ contact region 2236 serving as a body contact for thetransistor may be formed in the N-type well 2238. N-type well 2250represents an optional well which may increase the threshold voltage atwhich the transistor 2218 breaks down.

The transistor 2218 also includes P-type wells 2228 and 2234. A sourceregion 2226 may be formed in the P-type well 2228 and a drain region2232 may be formed in the P-type well 2234. A source contact 2230contacts the source region 2226 and a drain contact 2240 contacts thedrain region 2232. The transistor 2218 also includes P-type wells 2246,2248, 2252, and 2254.

The pattern represented by reference 2244 is an example of a maskpattern for the P+ implant process for forming transistor 2218. Asshown, only part of the gate 2242 is doped P+.

The ultrasound transducer probes described herein may implement varioustypes of circuit components, at least some of which may be constructedusing the high voltage designs described in connection with FIGS. 19-22in those embodiments in which the ultrasound transducer probes are tooperate with high voltages. Various non-limiting examples are nowprovided.

FIG. 23 illustrates an example of a pulser using a high voltage NMOS andPMOS layout with a high voltage switch that may be used in someembodiments as an isolation switch. As shown, the pulser 2300 comprisesfour transistors 2302, 2304, 2306 and 2308. Transistors 2302 and 2304are NMOS transistors and transistors 2306 and 2308 are PMOS transistors,though it should be appreciated that substantially the same pulser maybe constructed by suitably reversing the polarities. The transistors mayhave thick gate oxides as indicated by the heavy black linesrepresenting the gates, and thus such transistors may be high voltagetransistors capable of withstanding the voltages of the magnitudespreviously described.

The transistors 2302 and 2306 are connected in series between a highvoltage VH and a reference potential, such as GND. Likewise, transistors2304 and 2308 are connected in series between the voltage VH and thereference potential. Transistors 2302 and 2304 are controlled byrespective enable signals Txp and Txn.

The output Vout of the pulser may be provided to an electrode of anultrasound element, for example ultrasound element 1002. A secondelectrode of the ultrasound element 1002 may be connected to a referencepotential, such as electrical ground. The ultrasound element 1002 may beconnected to a receive circuitry module 2312 of the types previouslydescribed herein via a transistor switch 2310. The transistor switch2310 may be a high voltage transistor switch and may be controlled by anenable signal rx_en to isolate the receive module 2312 from the highvoltage.

The pulser 2300 may be disabled by setting Txp=0, Txn=1. Then, the valueof Txn may be set to Txn=0. The PMOS transistors 2306 and 2308 will holdstate as long as the Vout node stays within the low voltage rails of thecircuit.

FIGS. 24A and 24B illustrate pulser configurations which may be used tosupport voltages two times and four times as great as the voltagesupported by the pulser 2300, respectively. To produce a pulser whichcan sustain twice the voltage VH, i.e., to sustain 2VH, the pulser 2402of FIG. 24A may be used. As shown, the pulser 2402 additionallycomprises NMOS transistors 2403 and 2404, as well as PMOS transistors2406 and 2408. The gates of transistors 2403 and 2406 are tied togetherand configured to receive the voltage VH, as are the gates oftransistors 2404 and 2408.

To produce a pulser which can sustain four times the voltage VH, i.e.,to sustain 4VH, the pulser 2410 shown in FIG. 24B may be used. Thepulser 2410 includes NMOS transistors 2411 a and 2411 b and PMOStransistors 2411 c and 2411 d. In addition, the pulser 2410 comprisesNMOS transistors 2412, 2414, 2416, and 2418. None of the illustratedtransistors has a thick gate oxide. Transistors 2412 and 2416 areconnected in series with their gates electrically tied together.Likewise, transistors 2414 and 2418 have their gates electrically tiedtogether. An ultrasound element 2420 has a first terminal 2422 connectedbetween transistors 2416 and 2412 and a second terminal 2424 connectedbetween transistors 2414 and 2418. The terminals 2422 and 2424 aredriven with an H-bridge circuit.

FIGS. 25A-25B show examples of pulser circuits that can sustain highvoltages but which do not utilize a receive isolation switch. The pulser2502 of FIG. 25A includes an NMOS transistor 2504 having a thick gateoxide and controlled by an input signal Txn. The drain of the transistor2504 is coupled to a first electrode of an ultrasound element 1002 andalso to a resistor 2506, which has its other terminal configured toreceive the high voltage VH. The transistor 2504 operates as a highvoltage NMOS pull down device. The resistor 2506 may be defined by anN-type well in a P-type substrate or by nonsilicided polysilicon onfield oxide (FOX), as non-limiting examples.

The first electrode of the ultrasound element 1002 in FIG. 25A isconnected to the resistor 2506 and may be automatically biased when theultrasound element is operated in a receive mode. The second electrodeof the ultrasound element 1002 is directly connected to receivecircuitry module 2312 in FIG. 25A. Such a configuration may producelower parasitics than the structures of FIGS. 24A and 24B. The secondelectrode of the ultrasound transducer probe is also connected to groundvia an NMOS transistor 2508 actuated with transmit enable signal Tx_en.

FIG. 25B illustrates another example of a pulser which lacks a receiveisolation switch. The pulser 2510 includes a cascaded transistorarrangement with transistors 2504 and 2512. The cascaded arrangementallows the pulser 2510 to sustain twice the voltage (2VH) sustained bythe pulser 2502 of FIG. 25A. Transistor 2512 is controlled by voltageVH.

FIG. 26A shows an example of a time-interleaved single slope ADC that,in some embodiments, may be employed as one or more of the ADCs of anultrasound transducer probe referenced herein, for example as ADC 1020.In the illustrated example, N parallel ADCs are used for one channel totake alternating samples such that the sampling frequency of each ADC ismuch lower than the Nyquist criterion. Such single slope ADCs may, forexample, allow large-scale sharing of resources, such as bias, ramp, andgray counter. Such an ADC approach may thus provide a highly scalable,low power option.

As shown, the ADC 2600 may include a plurality of sample & hold circuits2602 a, 2602 b, 2602 c . . . corresponding to different receive channelsof an ultrasound transducer probe. The sample and hold circuits mayreceive a plurality of switching signals, illustrated collectively asS(*) via a switch signal input bus. The switching signals may controlthe sample and hold circuits to generate multiple (in this case five)samples per receive channel. The five samples per receive channel may beoutput from the sample and hold circuits to a comparator block 2604,which may also receive a ramp signal from a ramp circuit 2606. The rampcircuit 2606 is enabled by a signal ramp_en.

The comparator block 2604 compares the sampled values from the sampleand hold circuits to the ramp signal and generates five correspondingoutput values provided in parallel per receive channel. The outputs ofthe comparator block 2604 are provided to latches 2608, which arelatched by a counter 2610. The counter 2610 is enabled by a signalcount_en. The latches 2608 output digital signals corresponding to therespective channels, i.e., dout0 for channel 0, dout1 for channel 1,dout2 ₂ for channel 2, etc. The digital signals represent serial digitaloutputs.

FIG. 26B illustrates a timing diagram for the signal ramp_en, count_en,and ramp (the output of the ramp circuit 2606). As shown, the ramp_enand count_en signals may transition high at approximately the same time,triggering an increase in the ramp signal. The count_en signal may thentransition low at which time the ramp signal plateaus. When the ramp_ensignal subsequently transitions low the ramp signal does the same.

FIG. 27 expands on the sample and hold circuits and comparators of FIG.26A. In particular, FIG. 27 illustrates a portion of a single sample andhold circuit (e.g., sample and hold circuit 2602 a) and thecorresponding comparators 2604. The data from the receive channel(receive channel 0 in this case) is provided to a set of switches 2702controlled by respective switching signals S1-S6. In some embodiments, atotal of ten such switches may be provided to produce the five samplesfrom the sample and hold circuit 2602 a, but only six are shown forsimplicity. The switches 2702 capture samples of the signal from channel0 on respective capacitors 2706.

Switches 2704 may also be provided and are closed in any specifiedsequence to provide the values from the capacitors 2706 to an input ofthe comparators 2708. The comparators 2708 also receive the ramp signalof FIG. 26A. The outputs of the comparators 2708 correspond to theoutputs of comparator block 2604 of FIG. 26A.

FIG. 28A shows an example of a time shared high speed ADC that, in someembodiments, may be employed as one or more of the ADCs referencedherein for use in an ultrasound transducer probe, for example as ADC1020. Such an ADC may, for example, employ a pipelined,successive-approximation-register (SAR), or flash architecture. Becausea single high speed ADC having such an architecture may be used tosample N channels, such an ADC may significantly reduce arearequirements.

As shown, the ADC 2802 may be configured to receive data from aplurality of channels (i.e., receive channels of an ultrasoundtransducer probe) including channel 0 and channel 1. A capacitor C0 maybe coupled between a switch SW0, controlled by signal S5, and ground.Switch SW1, controlled by signal S0, may be operable to connect the ADC2802 suitably to receive data from channel 0.

Channel 1 may be coupled to the ADC 2802 via switches SW2 and SW3,controlled by signals S5 and S1, respectively. A capacitor C1 may becoupled between the switch SW2 and a reference voltage, such as ground.A switch SW4, controlled by signal S3, may also be provided to connectthe input of the ADC 2802 directly to the reference voltage, e.g.,ground.

FIG. 28B illustrates an exemplary timing diagram for operation ofswitches SW0, SW1, SW2, and SW3. A channel period is defined as having aduration from the beginning of one pulse of the signal S5 to thebeginning of a second pulse. A converter period is defined as thebeginning of one pulse of the signal S0 to the beginning of the nextpulse of signal S1.

The high voltage CMOS circuitry described herein may be configured todrive voltages higher than those conventionally attainable with CMOScircuitry, and to provide high voltages at deep submicron nodes. In someembodiments, voltages up to approximately 10 V may be supported ordriven, up to approximately 20 V may be supported or driven, up toapproximately 30 V may be supported or driven, up to approximately 40 Vmay be supported or driven, up to approximately 50 V may be supported ordriven, up to approximately 60 V may be supported or driven, voltagesbetween 20 V and 120 V may be supported or driven, between 30 V and 80V, between 40 V and 60 V, or any other suitable voltage within thoseranges, or other suitable voltages, as non-limiting examples.

As described previously, embodiments of the present application providean ultrasound transducer probe having one or more pulser circuits. Whenoperating an ultrasound transducer probe at high voltages, such as thosedescribed in connection with FIGS. 19-28B, having a single pulserconnected to an ultrasound element may create difficulties by requiringthe pulser to create very large voltage swings. For instance, the pulserconfiguration of FIG. 10 may require the pulser to create very largevoltage swings if the ultrasonic transducers are to be operated at highvoltages. To address this potential drawback of the circuitconfiguration of FIG. 10, an alternative configuration utilizing twopulsers per ultrasound element may be used in some embodiments. FIG. 29Aillustrates an example.

As shown, the circuit 2900 includes the ultrasound element 1002, thewaveform generator 1008 and two pulsers 2902 a and 2902 b. Pulser 2902 ais coupled to a first electrode of the ultrasound element 1002 andpulser 2902 b is coupled to a second electrode of the ultrasound element1002. An inverting amplifier 2906 is coupled to the input of the pulser2902 b to provide an inverted version of the waveform from waveformgenerator 1008. The circuit 2900 also includes a TIA 2904 and impedancesZ1 and Z2. A T/R switch 2908 couples the TIA 2904 to the ultrasoundelement 1002.

By utilizing the pulser configuration of FIG. 29A, each of the twopulsers need only generate half the voltage swing that would begenerated by the pulser in FIG. 10. Such a configuration may beadvantageous in those embodiments in which the ultrasonic transducers ofthe ultrasound transducer probe are not electrically tied together(e.g., do not all share a common electrode). The configuration of FIG.29A may be less advantageous in those embodiments in which theultrasonic transducers of the ultrasound transducer probe areelectrically tied together and biased together (e.g., when a commonelectrode, such as a top electrode, of the ultrasonic transducers isused to bias the transducers together).

The operation of the pulsers 2902 a and 2902 b can be further understoodby reference to FIG. 29B. FIG. 29B illustrates the operation of signalsVout1 and Vout2, corresponding to the output voltages of pulsers 2902 aand 2902 b, respectively, as a function of time. As shown, each of thetwo pulsers need exhibit approximately half the voltage swing betweenVout1 and Vout2 to effectively create a voltage swing from Vout1 toVout2. The pulsers 2902 a and 2902 b may be tri-level pulsers of thetypes previously described herein, and thus each may exhibit threevoltage levels in the output signal as shown in FIG. 29B.

Operating Modes

According to some aspects of the present application, the ultrasoundtransducer probes described herein may be used for ultrasound imaging,and when so used may be configured to operate in various imaging modes.Some embodiments provide for 2D and 3D imaging. When 2D ultrasoundimaging is performed, alternative manners may be utilized. According toone manner of 2D operation, the ultrasound transducer probe may collecta time domain signal echo across one dimension of the arrangement ofultrasonic transducers. An alternative method may involve collectingultrasound intensity data across two dimensions of the arrangement ofultrasonic transducers, but not measuring a time dimension. In someembodiments, a spectral domain signal may be used. In some embodiments,tomographic imaging may be utilized. The mode may be selected by a userin some embodiments. Non-limiting examples of imaging modes which may beutilized are now described.

One example of an imaging mode which may be exhibited is B-mode imaging.Plane wave imaging, virtual source imaging, all-pairs imaging, andfocused beam imaging are all examples of B-mode imaging which may beimplemented according to various embodiments.

Another imaging mode which may be used is M-mode imaging. This includessingle line and multi-line M-mode imaging according to some embodiments.

Doppler imaging may also be performed with the ultrasound transducerprobes according to various embodiments. Pulsed and vector flow Dopplerimaging are examples of Doppler modes which may be implemented.

Shear wave imaging is another example of an imaging mode which may beimplemented.

Harmonic imaging is another example of an imaging mode which may beimplemented. Pulse inversion, 3-pulse inversion, and coded excitationoperating schemes are enhancements to harmonic imaging which may also beimplemented.

Verberation flow imaging (V-flow) may also be used in some embodiments.

The ability to exhibit such varied imaging modes may be due at least inpart to the configurability of the ultrasound transducer probes. Thetransmit operation of an ultrasound transducer probe of the typesdescribed herein may be flexible. For example, the transmit operationmay be controlled by parameters which are selectable, such as theparameters of a programmable waveform generator of the types describedherein. For instance, the delay, amplitude, length, initial phase,initial frequency, and/or ramp rate of a desired excitation may beprogrammed into a waveform generator. In some embodiments, theparameterization may be substantially or fully arbitrary. Control overthe start and stop of transmit operations may be provided in anysuitable manner, such as with an enable signal. The transmit voltagesmay be adjustable.

The receive operation of ultrasound transducer probes of the typesdescribed herein may also be flexible, exhibiting significantconfigurability. For example, as described in connection with FIGS. 9and 10, the manner in which signals are read out from ultrasoundelements may include electrically tying multiple ultrasound elements tocommon receive circuitry, or alternatively each ultrasound element mayhave its own dedicated receive circuitry. Thus, the amount of ultrasounddata generated by an ultrasound transducer probe may be selectable.

The use of external links for communicating between an ultrasoundtransducer probe and an external device may be configurable according toaspects of the present application and may be selected based on anintended imaging mode. For example, the maximum number of availablelinks may be utilized in embodiments in which it is desirable tomaximize data output from the ultrasound transducer probe, and may allowfor large quantities of data to be offloaded from the ultrasoundtransducer probe without averaging or other data reduction processing.Alternatively, fewer than the maximum number of links available may beutilized in embodiments in which maximum data is not needed. Forexample, half the links or only a single link may be utilized. In suchembodiments, averaging of data may be implemented to facilitateoffloading of a sufficient amount of data to support desired end userapplications, such as ultrasound imaging.

The data format processed by the ultrasound transducer probe may also beconfigurable. For example, full waveforms may be processed in someembodiments. Alternatively, peak values may be processed, which mayallow for a reduction in the data processing requirements of theultrasound transducer probe.

Various additional parameters of the ultrasound transducer probeoperation may be configurable. Such parameters include the receivewindow, channel subselection, the TGC configuration, data reductionparameters such as averaging or data dropping parameters, pulserepetition intervals, event sequencing intervals, quantizerconfigurations, and filter taps, among others.

Thus, it should be appreciated that the architecture of the ultrasoundtransducer probe in terms of the ultrasound transducers and controlcircuitry may facilitate use of the ultrasound transducer probe in avariety of modes of operation for a variety of applications.Accordingly, ultrasound transducer probes according to one or moreaspects of the present application may represent sophisticated andversatile ultrasound devices configurable to create an ultrasoundtransducer probe geometry of choice.

Moreover, as has been described previously, for example in connectionwith FIGS. 2A-2G, ultrasound transducer probes serving as repeatableunits that are capable of being tiled are provided. Such transducerprobes may be fabricated, in some embodiments, by tiling and dicingtogether multiple instances of an ultrasound transducer probe to createan ultrasound transducer probe capable of exhibiting desired imagingfunctionality. In some embodiments, individual instances of anultrasound transducer probe may be diced and subsequently tiled andinterconnected suitably to form an ultrasound transducer probe withdesired imaging functionality. Therefore, flexibility in the ultrasounddevice achieved and the imaging capabilities of that ultrasound deviceare provided by the simple and flexible manner of fabricating multipleinstances of a repeatable ultrasound unit.

Transducer

The ultrasonic transducers of ultrasound transducer probes of the typesdescribed herein may be any suitable ultrasonic transducers, and in someembodiments may have features which facilitate creation of stand-aloneultrasound transducer probes exhibiting a high degree of integration. Insome embodiments, the ultrasonic transducers may be compatible with aCMOS substrate, thus allowing them to be monolithically formed on a CMOSsubstrate with CMOS ICs. In this manner, an integrated device (e.g., anultrasound system-on-a-chip) may be formed.

In some embodiments, the ultrasonic transducers may be CMOS ultrasonictransducers (CUTs). A CUT may, for example, include a cavity formed in aCMOS wafer, with a membrane (or diaphragm) overlying the cavity, and insome embodiments sealing the cavity. Electrodes may be provided tocreate a transducer cell from the covered cavity structure. The CMOSwafer may include integrated circuitry to which the transducer cell maybe connected. The transducer cell and CMOS wafer may be monolithicallyintegrated, thus forming an integrated ultrasonic transducer cell and ICon a single substrate (the CMOS wafer).

CUTs are not the only type of ultrasonic transducer which may allow forintegration of the transducer with an IC. In some embodiments, theultrasonic transducers may be capacitive micromachined ultrasonictransducers (CMUTs).

Not all embodiments are limited to employing CUTs or CMUTs in anultrasound transducer probe of the types described herein. Some aspectsof the present application apply to ultrasound transducer probesirrespective of the type of ultrasonic transducer implemented.

According to an aspect of the present application, ultrasonictransducers are formed above a thick top metal layer of a CMOSsubstrate. Ultrasound transducer probes according to aspects of thepresent application may include an arrangement of ultrasonic transducerson a CMOS substrate. The arrangement of ultrasonic transducers may spana distance which is relatively long in terms of signal transmissionproperties, which may run a risk of exhibiting relatively highimpedances, and thus performance degradation. The problem may beenhanced if the ultrasound transducer probe comprises a CMOS substratewhich is wider than it is tall (e.g., a wide aspect ratio substrate),which, as previously described, may be used in some embodiments. Use ofa thick top metal layer of the CMOS substrate for power and groundsignal distribution may at least partially mitigate the difficultiesassociated with long signal paths on the CMOS substrate. A metal layermay be “thick” when having a thickness greater than approximately 0.5microns, for example having a thickness between approximately 0.5microns and approximately 10 microns. A thick top metal layer may bereferred to in some embodiments as an ultra-thick redistribution layer.

When a thick top metal layer of the CMOS substrate is reserved for powerand ground signal distribution, an ultrasonic transducer formed abovesuch a thick top metal layer may be connected to the thick top metallayer using vias or other suitable structures. CUTs and CMUTs oftenemploy two or more electrodes. Connection of the electrode(s) of theultrasonic transducer to the thick top metal layer may be made with oneor more vias.

While some aspects of the present application implementing a metal layerfor power and ground signal distribution utilize a thick top metal layerfor such distribution, not all aspects are limited in this respect. Forexample, a top metal layer which is not necessarily thick may beemployed in some embodiments. Moreover, the metal layer need not be thetop metal layer in all embodiments. Various examples of ultrasonictransducers according to aspects of the present application are nowillustrated and described. Each is described as including a top metallayer, which may be thick in any of the illustrated embodiments.

Transducer Example 1

Several examples of ultrasonic transducers integrated with a CMOSsubstrate and formed above a (top) metal layer of the CMOS substrate arenow described. FIG. 30A illustrates a first example. The device 3000includes a CMOS substrate 3002 on which is formed an ultrasonictransducer (e.g., a CUT) 3004.

The CMOS substrate 3002 represents a non-limiting example of a suitableCMOS substrate, and it should be appreciated that alternative CMOSsubstrates may be utilized. In the example of FIG. 30A, the CMOSsubstrate 3002 includes a semiconductor substrate 3006, which may be asilicon substrate (e.g., a bulk silicon wafer), or any other suitablesemiconductor substrate. An insulating layer 3008, for example of SiO₂,is on the semiconductor substrate 3006. A conductive layer 3010 is onthe insulating layer 3008 and covered by a second insulating layer 3012.The conductive layer 3010 may be a metallization layer in someembodiments, and may be patterned as shown to form a plurality of signallines. For example, the conductive layer 3010 may be formed of aluminumwith bottom and top liner layers. The insulating layer 3012 may be SiO₂or any other suitable insulating material.

A top metal layer 3014 is included with the CMOS substrate 3002, havinga thickness T_(m). The top metal layer 3014 may be a thick metal layerin some embodiments, and in such embodiments the thickness T_(m) may bebetween approximately 0.5 microns and approximately 10 microns, betweenapproximately 2 microns and approximately 5 microns, any range or valuewithin such ranges, or any other suitable value for providing decreasedresistivity to facilitate functioning of the top metal layer 3014 as asignal distribution layer. The top metal layer 3014 may be patterned tocreate an island 3017, described further below. In addition, stressrelieving openings or cuts may optionally be formed in the top metallayer 3014.

In some embodiments, the top metal layer 3014 may have liner layersabove and below, such as liners 3013 a and 3013 b. For example, the topmetal layer 3014 may be formed of aluminum with a TiN liner above andbelow. In some embodiments, a liner may be a multi-layer structure, forexample being formed of two or more metals. As a non-limiting example,liner 3013 b may include a first layer of titanium nitride (TiN) and asecond layer of silicon oxynitride (SiON). SiON may be used in someembodiments as a top layer of a metallization layer since it may serveas an anti-reflective coating for photolithography purposes. Any linerincluded below and/or above the top metal layer may be a thin film.

The CMOS substrate 3002 further comprises an insulating layer 3016. Theinsulating layer 3016 may be formed of any suitable insulating material,a non-limiting example of which is SiO₂.

The ultrasonic transducer 3004 includes several components. A membrane3018 overlies a cavity 3020 in the CMOS substrate 3002. In someembodiments, the membrane 3018 seals the cavity 3020, for instanceproviding a vacuum. A conductive layer 3030 formed of any suitableconductive material to provide electrical connection to a bottom side ofthe membrane 3018 is also provided. As a non-limiting example, theconductive layer 3030 may be formed of a thin film, for example beingformed of TiN.

The cavity 3020 overlies an electrode 3022 which may be considered abottom electrode of the ultrasonic transducer 3004. The electrode 3022may be formed of any suitable conductive material. In some embodiments,the electrode 3022 may be formed of a thin film material, such as TiN.In some embodiments, TiN may be used as an etch stop for etching thecavity 3020 in the CMOS substrate 3002. Alternatives are possible.

The sidewalls of the cavity 3020 are formed by conductive spacers 3024,which may perform various functions. For example, the conductive spacers3024 may at least partially define the depth of the cavity 3020. Theconductive spacers, sometimes in combination with other structures, mayelectrically connect the membrane 3018 to the top metal layer 3014. Theconductive spacers 3024 may be formed of any suitable conductivematerial. In some embodiments, the conductive spacers 3024 may be formedof TiN, although other conductive materials may alternatively be used.

The device 3000 also includes multiple vias, disposed in the insulatinglayer 3016. Three such vias 3026 a-3026 c are illustrated. The vias 3026a-3026 c may be formed of any suitable conductive material, anon-limiting example of which is tungsten (W). The vias 3026 a and 3026c may provide electrical connection between the top metal layer 3014 andconductive contacts 3028 a-3028 b, respectively, on which the conductivespacers 3024 are disposed. The conductive contacts 3028 a-3028 b may beformed of any suitable conductive material, a non-limiting example ofwhich is TiN. The via 3026 b electrically connects the electrode 3022 tothe island 3017 of the top metal layer 3014.

As shown, additional insulating layers 3032 and 3034 are included in thedevice 3000. The insulating layer 3034 may substantially cover thebottom electrode 3022 and may provide electrical insulation. Insulatinglayers 3032 and 3034 may be formed of any suitable insulating material,a non-limiting example of which is SiO₂.

Additional structures of the device 3000 may provide electricalconnection between the substrate 3006 and the electrode 3022. Forinstance, vias 3007 and 3009 may connect the electrode 3022 to thesubstrate 3006 by way of the conductive layer 3010. The vias 3007 and3009 may be formed of any suitable conductive materials, a non-limitingexample of which is tungsten.

The device 3000 may have any suitable dimensions. For example, thecavity 3020 may have a depth DC between approximately 0.05 microns andapproximately 10 microns, between approximately 0.1 microns andapproximately 5 microns, between approximately 0.5 microns andapproximately 1.5 microns, any depth or range of depths in between, orany other suitable depth.

The width WC of the cavity 3020 may be between approximately 5 micronsand approximately 500 microns, between approximately 20 microns andapproximately 100 microns, may be approximately 30 microns,approximately 40 microns, approximately 50 microns, any width or rangeof widths in between, or any other suitable width. In some embodiments,the width may be selected to maximize the void fraction, i.e., theamount of area consumed by the cavity compared to the amount of areaconsumed by surrounding structures. The width dimension may also be usedto identify the aperture size of the cavity, and thus the cavities mayhave apertures of any of the values described above or any othersuitable values.

It can be seen from FIG. 30A that the electrode 3022 may not be as wideas the cavity 3020. Such a configuration may be desirable when thesidewalls of the cavity are formed of a conductive material, to preventelectrical breakdown between the bottom electrode 3022 of the ultrasonictransducer and the cavity sidewalls. However, not all embodiments arelimited in this respect, as ultrasonic transducers usable in ultrasoundtransducer probes of the present application may have bottom electrodesthat are as wide as, or wider than, the cavity.

The membrane thickness T1 (e.g., as measured in the direction generallyparallel to the depth DC) may be less than 100 microns, less than 50microns, less than 40 microns, less than 30 microns, less than 20microns, less than 10 microns, less than 5 microns, less than 1 micron,less than 0.1 microns, any thickness or range of thicknesses in between,or any other suitable thickness. The thickness may be selected in someembodiments based on a desired acoustic behavior of the membrane, suchas a desired resonance frequency of the membrane.

In some embodiments, the cavity dimensions and/or the membrane thicknessof any membrane overlying the cavity may impact the frequency behaviorof the membrane, and thus may be selected to provide a desired frequencybehavior (e.g., a desired resonance frequency of the membrane). Forexample, it may be desired in some embodiments to have an ultrasonictransducer with a center resonance frequency of between approximately 20kHz and approximately 200 MHz, between approximately 1 MHz andapproximately 10 MHz, between approximately 2 MHz and approximately 5MHz, between approximately 50 kHz and approximately 200 kHz, ofapproximately 2.5 MHz, approximately 4 MHz, any frequency or range offrequencies in between, or any other suitable frequency. For example, itmay be desired to use the devices in air, gas, water, or otherenvironments, for example for medical imaging, materials analysis, orfor other reasons for which various frequencies of operation may bedesired. The dimensions of the cavity and/or membrane may be selectedaccordingly.

Also, it should be appreciated that the cavity 3020, and more generallythe cavities of any embodiments described herein, may have variousshapes, and that when multiple cavities are formed not all cavities needhave the same shape or size. For example, when considering a top view ofthe cavity 3020, the cavity may have a square aperture, a circularaperture (e.g., as in FIG. 5B), a hexagonal aperture, an octagonalaperture, or any other suitable shape.

It should be appreciated from FIG. 30A that an ultrasonic transducer maybe integrated with a CMOS substrate and that electrical contact may bemade between upper and lower electrodes of the ultrasonic transducer anda top metal layer of the CMOS substrate with one or more vias. Also, thetop metal layer (e.g., top metal layer 3014) of the CMOS substrate maybe suitably patterned or segmented as shown to provide electricalisolation between the bottom electrode 3022 and the conductive layer3030 of the ultrasonic transducer. For example, the island 3017 mayprovide electrical isolation between the electrode 3022 and theconductive layer 3030.

As previously described, the conductive layer 3010 may be patterned toform a plurality of signal lines. The top metal layer 3014 may, in someembodiments, shield the signals lines from the ultrasonic transducer3004. Such a configuration may facilitate transmission of signals on theCMOS substrate 3002.

It should be appreciated that device 3000 illustrates an example of adevice including embedded conductive structures in a CMOS substrateproviding electrical connection to the membrane of an ultrasonictransducer. For example, vias 3026 a-3026 c are embedded in the CMOSsubstrate and form at least part of respective electrical paths fromconductive layers of the CMOS substrate 3002 to electrodes of theultrasonic transducer 3004.

Transducer Fabrication Example

Various processes may be used to form devices including ultrasonictransducers integrated with a CMOS substrate of the types describedherein. FIG. 37 is a flow chart illustrating an example. The method 3700includes stage 3702 at which a CMOS wafer is processed to form a topmetal layer, which optionally may be a thick top metal layer.

At stage 3704, the CMOS wafer may be processed to form one or more viasextending above the top metal layer. Such vias may be used to provideelectrical connection between the top metal layer and an electrode of asubsequently formed ultrasonic transducer.

At stage 3706, the CMOS wafer may be prepared for wafer bonding with atransfer wafer. Such preparation may involve, for example, planarizationand surface treatment.

At stage 3708, the CMOS wafer and the transfer wafer may be bonded usinga low temperature bonding process. The transfer wafer may include one ormore layers forming a membrane of an ultrasonic transducer of the bondeddevice. In some embodiments, the bonding may seal one or more cavitiesin the CMOS wafer.

At stage 3710, the transfer wafer may be thinned from the backside toleave the desired membrane.

It should be appreciated that variations on the method 3700 arepossible. For example, stage 3704 may be performed after wafer bondingin some embodiments.

A process for fabricating the device 3000 consistent with the method3700 is now illustrated and described, beginning with FIG. 30B. It willbe appreciated that various processing steps may be performed prior tothe stage illustrated in FIG. 30B to arrive at the illustratedstructure. For instance, insulating layer 3008 may be formed on thesemiconductor substrate 3006 and then patterned to allow formation ofvia 3007, for example by deposition of tungsten. Conductive layer 3010may then be formed and patterned. According to an embodiment, theconductive layer 3010 may be formed of aluminum and may include bottomand top liner layers, for example of TiN, SiON, both, or any othersuitable liner material. According to an embodiment, a layer of TiN anda layer of SiON may be formed on the top surface of conductive layer3010. The conductive layer 3010 may be patterned as shown, for exampleto form a plurality of wiring lines.

Subsequently, insulating layer 3012 may be formed, for example bysuitable deposition and planarization. The insulating layer 3012 maythen be patterned and filled with conductive material (e.g., tungsten)to form via 3009. An etch back step or other planarization step may thenbe performed to provide a substantially planar upper surface.

The liner 3013 a may then be deposited, followed by deposition of thetop metal layer 3014. The liner 3013 b may then be deposited.

As shown in FIG. 30B, the top metal layer 3014 may then be patterned toform a plurality of openings 3015, thus defining the island or othersegment 3017. The patterning may involve any suitable etch technique fora (thick) metal layer, and as shown may involve etching through theentire thickness of the top metal layer 3014. The island 3017 may beelectrically isolated from other segments of the top metal layer 3014 sothat the island 3017 may be used to make contact to an electrode of theultrasonic transducer 3004 as shown in FIG. 30A.

Referring to FIG. 30C, the insulating layer 3016 may then be formed bydepositing an insulating material to fill the openings 3015, for exampleusing a high density plasma (HDP) deposition (e.g., HDP deposition ofSiO₂). The insulating material may then be planarized and patterned toform openings which may be filled with a conductive material to createvias 3026 a-3026 c. The conductive material deposited to fill theopenings in the insulating layer 3016 to form the vias 3026 a-3026 c maybe deposited conformally, for example using chemical vapor deposition(CVD).

The conductive material may then be etched back to have an upper surfacesubstantially even with an upper surface of the insulating layer 3016,thus completing the structure shown in FIG. 30C.

As shown in FIG. 30D, a conductive layer may be deposited and patternedto form the bottom electrode 3022 and the conductive contacts 3028a-3028 b. Any suitable deposition or formation technique may be used toform the conductive layer, and any suitable etching technique may beused to pattern the conductive layer to achieve the structureillustrated in FIG. 30D. In some embodiments, the conductive materialused to form electrode 3022 and conductive contacts 3028 a-3028 b is amaterial suitable for thin film deposition, such as TiN. The illustratedmanner of forming the bottom electrode 3022 and conductive contacts 3028a-3028 b from a common conductive layer may represent a valuable processsimplification in some embodiments compared to if separate depositionswere used to form those structures.

Next, referring to FIG. 30E, insulating layer 3032 may be formed, forexample by depositing an insulating material conformally on thestructure of FIG. 30D, to cover the bottom electrode 3022 and conductivecontacts 3028 a-3028 b. Then, the insulating layer 3032 may be etchedback using any suitable etch technique or planarization technique, forexample chemical mechanical polishing (CMP), such that the insulatinglayer 3032 has an upper surface below the upper surfaces of theelectrode 3022 and conductive contacts 3028 a-3028 b, as shown. Aspreviously described, the insulating layer 3032 may be formed of anysuitable insulating material, a non-limiting example of which is SiO₂.

Then, insulating layer 3034 may be deposited conformally and etched backto provide a desired thickness. The insulating layer 3034 may cover thebottom electrode 3022 and conductive contacts 3028 a-3028 b at thisstage of processing. The thickness of insulating layer 3034 may assumeany suitable value for covering the bottom electrode 3022 to provideelectrical insulation between the bottom electrode 3022 and theconductive layer 3030 of FIG. 30A in the event that the conductive layer3030 comes into contact with the bottom electrode 3022.

Referring now to FIG. 30F, openings may be formed in the insulatinglayer 3034 above the conductive contacts 3028 a-3028 b using anysuitable patterning technique. The conductive spacers 3024 may then beformed by depositing a conductive material, planarizing, and patterningthe conductive material, as an example. The conductive spacers 3024 maybe formed to have a desired thickness for the cavity 3020 shown in FIG.30A.

Surface treatment may then be performed as appropriate to prepare theCMOS substrate for bonding to a transfer wafer. Referring to FIG. 30G, awafer 3042 may be bonded with the CMOS substrate 3002 to cover, and insome instances seal, the cavity 3020. The wafer 3042 may be considered asecond wafer, in addition to the CMOS wafer, and may also be referred toas a transfer wafer or handle wafer in some embodiments since it may,for example, transfer a membrane to the CMOS substrate. It should beappreciated, therefore, that fabrication of ultrasonic transducers mayinvolve wafer level processing, including wafer level bonding, which mayfacilitate cost effective fabrication of large numbers of the ultrasonictransducers.

The wafer 3042 may include the membrane 3018 and conductive layer 3030,and thus may function as a transfer wafer to transfer the membrane 3018to the CMOS substrate 3002. The wafer 3042 may additionally include asubstrate or other base layer 3044 and an insulating layer 3046.

Non-limiting examples of suitable transfer wafers are described furtherbelow. In general, the second wafer may be any suitable type of wafer,such as a bulk silicon wafer, a silicon-on-insulator (SOI) wafer, or anengineered substrate including a polysilicon or amorphous silicon layer(e.g., membrane 3018) with an insulating layer between a single crystalsilicon layer (e.g., substrate 3044) and the polysilicon or amorphoussilicon layer. For example, the substrate 3044 may be a bulk siliconsubstrate and the insulating layer 3046 may be SiO₂. The insulatinglayer 3046 may represent a buried oxide (BOX) layer. The membrane 3018may be single crystal silicon, polysilicon, or amorphous silicon, asnon-limiting examples, and in some embodiments may be doped to providedesired conductivity. In some embodiments, the membrane 3018 may bedegeneratively doped, and in some embodiments may be P+ doped. Aspreviously described, the conductive layer 3030, when included, may beformed of TiN as a non-limiting example.

The bonding process used for bonding the CMOS substrate 3002 and thewafer 3042 may be a low temperature bonding process suitable to preservestructures such as silicon circuitry on the CMOS substrate. For example,the bonding may not exceed 450° C. In some embodiments, the temperatureof the bonding process may be between approximately 200° C. and 450° C.,between approximately 300° C. and approximately 400° C., less than 250°C., any temperature(s) within those ranges, any other temperaturedescribed herein for low temperature bonding, or any other suitabletemperature. Thus, damage to the metallization layers on the CMOSsubstrate, and any ICs on the CMOS substrate, may be avoided.

The completed device 3000 of FIG. 30A may be achieved from the structureof FIG. 30G by removing the substrate 3044 and insulating layer 3046.For instance, in some embodiments, the wafer 3042 may be thinned fromthe backside. Such thinning may be performed in stages. For example,mechanical grinding providing coarse thickness control (e.g., 10 microncontrol) may initially be implemented to remove a relatively largeamount of the bulk wafer (e.g., substrate 3044). In some embodiments,the thickness control of the mechanical grinding may vary from coarse tofine as the thinning process progresses. Then, CMP may be performed onthe backside, for example to get to a point close to the membrane 3018.Next, a selective etch, such as a selective chemical etch, may beperformed to stop on the membrane 3018. In some embodiments, themembrane 3018 itself may be thinned. Other manners of thinning are alsopossible.

While FIG. 30A illustrates a non-limiting example of an embodiment of anultrasonic transducer formed above a top metal layer of a CMOS substrateand suitable for use in ultrasound transducer probes according to one ormore embodiments of the present application, it should be appreciatedthat alternative configurations are possible. Various alternativedevices and the processes for fabricating such devices are nowdescribed.

Transducer Example 2

FIG. 31A illustrates a device 3100 including an ultrasonic transducer3102 formed above a top metal layer of a CMOS substrate 3104 andincluding various optional features in addition to those of the device3000. For example, the ultrasonic transducer 3102 has a pistonconfiguration. Namely, the ultrasonic transducer 3102 includes a pistonmembrane including the membrane 3018 with a thick center portion 3106.The piston configuration of the ultrasonic transducer 3102 may bedesirable in some embodiments to provide beneficial operatingcharacteristics of the ultrasonic transducer. For example, use of apiston configuration as shown may provide better frequency operation,power characteristics, or other operating characteristics in at leastsome embodiments. The thickness of the center portion 3106 may be anysuitable value for providing such desired operating characteristics. Forexample, the thickness of the center portion 3106 (including thethickness of membrane 3018) may be between 1 micron and approximately100 microns, between approximately 10 microns and approximately 50microns, any value within such ranges, or any other suitable values.

The center portion 3106 may be formed of any suitable material. As anon-limiting example, the center portion 3106 may be formed of TiN.However, other conductive, semiconductor, or insulating materials may beused. In some embodiments, it may be desirable for the center portion3106 to be formed of a different material than membrane 3018 to allowfor the piston membrane to exhibit target behavior with respect tocharacteristics such as flexibility, capacitive operation, androbustness, among other possible characteristics relevant to operationof the transducer.

In addition, the device 3100 includes a membrane stop 3108. In someembodiments, the membrane stop, which may be formed of any suitablematerial, such as an insulating material (e.g., SiO₂), may function asan isolation post and may provide various benefits. Membrane stops mayeffectively alter the depth of a cavity such that a membrane may contactthe bottom of the cavity (referred to as collapse) more easily, and mayalter the frequency behavior of an ultrasonic transducer. Namely, whenthe membrane is pulled down far enough, it makes contact with the bottomof the cavity. Such operation may be advantageous since having themembrane hit or contact the bottom of the cavity can dampen certainresonant modes, thereby broadening the frequency response of thetransducer. However, there is a “charge trapping” effect, in whichcharge may end up deposited on the electrodes of the transducer, therebyaltering the operating characteristics of the transducer (e.g.,increasing the necessary bias voltage), and causing hysteresis. Membranestops may provide the benefit of “bottoming out” the membrane, whilesubstantially reducing the charge trapping effect and problems withhysteresis. Ultrasonic transducers with membrane stops may be morereliable after collapse than ultrasonic devices lacking such membranestops. Moreover, because the membrane stop may prevent the membrane fromcontacting the bottom-most part of the cavity, insulation need not beformed on the bottom surface of the cavity in all embodiments, which cantherefore reduce processing steps and time in fabricating an ultrasonictransducer. However, the insulator on the bottom surface of the cavitymay be used in case of unanticipated contact between the membrane andthe bottom of the cavity (despite any membrane stop) and/or to preventelectrical discharge across the cavity.

Membrane stops may be formed in different locations of an ultrasonictransducer. For example, membrane stops may be formed on the bottom of acavity of an ultrasonic transducer. In some embodiments, membrane stopsmay be formed on the bottom of a membrane of the ultrasonic transducer(e.g., on the bottom side of a membrane transferred from a transferwafer). In other embodiments, membrane stops may be formed on both thebottom of a cavity and the bottom of a membrane of an ultrasonictransducer.

The membrane stop 3108 may control how far the membrane 3018 can moverelative to the bottom electrode 3022, and may have any suitablethickness for providing such control. For example, the membrane stop3108 may have a thickness between approximately 5% and 30% of the cavitydepth, between approximately 10% and 20% of the cavity depth, or anyvalue within such ranges. An insulating layer 3110, for example formedof SiO₂, may substantially cover the membrane stop 3108 in addition tothe bottom electrode 3022.

The ultrasonic transducer 3102 also differs from the ultrasonictransducer 3004 in that the conductive spacers 3024 are replaced byconductive spacers 3112 that are formed by multiple distinct portions3114 and 3116. The conductive spacers 3112 provide electrical connectionfrom the membrane 3018 to the top metal layer 3014 together with theconductive contacts 3028 a-3028 b and the vias 3026 a and 3026 c. Theportions 3114 and 3116 may be formed of TiN or other suitable conductivematerials.

It should be appreciated that the device 3100 therefore representsanother example of a device configuration including embedded conductivestructures in a CMOS substrate providing electrical connection to themembrane of an ultrasonic transducer.

An example of a process for fabricating the device 3100 is nowdescribed. The process may proceed in substantially the same manner asthat previously described in connection with device 3000 up to theformation of insulating layer 3032. Then, an insulating layer may beconformally deposited and patterned to form membrane stop 3108. Next,insulating layer 3110 may be deposited and patterned to form openingsabove the conductive contacts 3028 a and 3028 b.

A conductive material may then be deposited, patterned and planarized asappropriate to form portion 3116 of the conductive spacers 3112. Surfacetreatment may be performed as appropriate to prepare the CMOS substratefor bonding to a transfer wafer.

Subsequently, as shown in FIG. 31B, a transfer wafer 3118 may be alignedand bonded with the CMOS substrate 3104. The transfer wafer 3118 mayinclude the portion 3114 and the center portion 3106 of the pistonmembrane. The bonding may be any type described herein, such as a lowtemperature bonding.

Then, the wafer 3118 may be processed in any suitable manner to removethe substrate 3044 and insulating layer 3046. For example, any of thetechniques described with respect to processing of such layers of thetransfer wafer 3042 may be utilized. In this manner, the final structureillustrated in FIG. 31A may be achieved.

Thus, it should be appreciated from FIG. 31A that an embodiment of thepresent application provides an ultrasonic transducer formed above a topmetal layer of a CMOS substrate, in which embedded conductive structuresin the CMOS substrate provide electrical contact to the membrane of theultrasonic transducer.

Transducer Example 3

FIG. 32A illustrates an example of another device 3200 having anultrasonic transducer 3202 formed above the top metal layer 3014 of theCMOS substrate 3002. As shown, the ultrasonic transducer 3202 has apiston membrane configuration. The device 3200 is another example of adevice including conductive features embedded in the CMOS substrate toprovide electrical connection to the membrane of an ultrasonictransducer.

As shown, the piston membrane 3204 includes a center region 3206 and aperipheral region 3208. The center region 3206 may be thicker than theperipheral region 3208, as illustrated, with the relative thicknesses ofthe two regions assuming any suitable value to provide desired operationof the ultrasonic transducer 3202.

The piston membrane 3204 may be formed of any suitable material. As anon-limiting example, the piston membrane 3204 may be formed of silicon,which may be doped in some embodiments to provide desired electricalconductivity. For example, in those embodiments in which the pistonmembrane 3204 is formed of silicon, the silicon may be doped with apositive dopant, such as phosphorus. As also shown, the center region3206 may have a width Wp substantially corresponding to the width Wb ofthe bottom electrode 3022, which may provide beneficial capacitivebehavior of the ultrasonic transducer. However, alternativeconfigurations are possible.

An example of a process for fabricating the device 3200 is nowdescribed. The process may proceed in substantially the same manner asthat previously described in connection with formation of device 3000 upthrough the point illustrated in FIG. 30F. Then, instead of bonding tothe transfer wafer 3042 of FIG. 30G, the CMOS substrate may be alignedand bonded with the transfer wafer 3210. The transfer wafer 3210 mayinclude the substrate 3044, the insulating layer 3046, the conductivelayer 3030, and an additional insulating layer 3212. The wafer 3210 mayalso include the piston membrane 3204.

The insulating layer 3212 may be formed of any suitable material. As anon-limiting example, the insulating layer 3212 may be formed of SiO₂ orany other suitable dielectric insulating material. In some embodiments,the insulating layer 3212 may be formed via tetraethyl orthosilicate(TEOS), though alternative processes may be used.

The bonding of CMOS substrate 3002 and transfer wafer 3210 may involveany suitable bonding process. For instance, a low temperature bondingprocess of the types described herein may be utilized.

Subsequently, substrate 3044, insulating layer 3046, and insulatinglayer 3212 may be removed in any suitable manner to arrive at thestructure of FIG. 32A. For example, wafer grinding, etching techniques,or any other suitable removal techniques may be used, such as thosedescribed previously for thinning of a wafer, such as wafer 3042.

Devices 3000-3200 represent non-limiting examples of devices includingultrasonic transducers having conductive sidewalls. Several examples ofultrasonic transducers formed on CMOS substrates and havingnon-conductive sidewalls are now illustrated and described.

Transducer Example 4

FIG. 33 illustrates a device 3300 including an ultrasonic transducer3302 formed above a top metal layer of a CMOS substrate 3304.Non-conductive spacers 3306 define a standoff of the membrane 3018 fromthe bottom of the cavity 3020. Conductive vias 3308 are formed in thenon-conductive spacer 3306. A suitable liner 3310 is included to preventmigration of the via material into the non-conductive spacer 3306. Forexample, the liner 3310 may be formed of TiN or any other suitableconductive lining material. The vias 3308 may be formed of a suitableconductive material, a non-limiting example of which is tungsten. Theultrasonic transducer 3302 also includes an insulating layer 3312covering the bottom electrode 3022. The non-conductive spacers 3306 andinsulating layer 3312 may both be formed of SiO₂, as a non-limitingexample.

As shown, the membrane 3018 makes direct contact with an upper surfaceof the via 3308. Thus, an electrical path from the membrane 3018 to thetop metal layer 3014 is provided by a combination of via 3308,conductive contact 3028 a, and via 3026 a.

An example of a process for fabricating the device 3300 is nowdescribed. The process may proceed in substantially the same manner asthat previously described in connection with the formation of device3000 up through the point illustrated in FIG. 30D.

Subsequently, an insulating layer may be deposited or otherwise formedand planarized in preparation of forming non-conductive spacers 3306.The insulating layer may be conformally deposited to cover the surfaceof the CMOS substrate, and then may be patterned to create trenches orother openings for the vias 3308. Then, the liner 3310 may be depositedin the trenches and the trenches filled with conductive material to formthe vias 3308. A planarization or etch back may optionally be performed.The insulating layer deposited to form the non-conductive spacers 3306may then be suitably patterned to form the non-conductive spacers.

Then, insulating layer 3312 may be deposited and the structure may beplanarized and treated in preparation for bonding, to remove theinsulating layer 3312 from the upper surfaces of the non-conductivespacers 3306. Next, a transfer wafer similar to the transfer wafer 3042,but lacking conductive layer 3030, may be aligned with and bonded to theCMOS substrate 3304. The substrate 3044 and insulating layer 3046 maythen be removed to achieve the device 3300.

Transducer Example 5

Another example of a device including an ultrasonic transducer above atop metal layer of a CMOS substrate is illustrated in FIG. 34. As shown,the device 3400 includes an ultrasonic transducer 3402 integrated with aCMOS substrate 3404. Vias 3406, which may be formed of tungsten or othersuitable conductive material, pass through the membrane 3018 and thenon-conductive spacers 3306 to make contact with the conductive contacts3028 a-3028 b. A liner 3408 may be provided and may be the same aspreviously described liner 3310.

The device 3400 further includes layers 3410 and 3412 which may servemultiple functions in the illustrated embodiment. For instance, thelayers 3410 and 3412 may passivate the upper surface of the via 3406.Additionally, the layers 3410 and 3412 may be patterned as shown tocreate a piston membrane in combination with membrane 3018. Thethicknesses of layers 3410 and 3412 may be selected to provide desiredoperating characteristics to the ultrasonic transducer 3402.

The layers 3410 and 3412 may be formed of any suitable materials, and insome embodiments are formed of insulating materials. For example, layer3410 may be SiO₂ and layer 3412 may be silicon nitride (Si₃N₄) accordingto a non-limiting example. However, alternative passivation materialsmay be used.

An example of a process for fabricating the device 3400 is nowdescribed. The process may proceed in substantially the same manner asthat previously described in connection with fabrication of device 3300except that formation of the vias 3308 may be omitted. Thus, themembrane 3018 may be bonded with the CMOS substrate 3404 without vias inplace connecting the membrane 3018 to the conductive contacts 3028 a and3028 b. The bonding may be a low temperature bond, for example of thetypes described previously herein.

Then, after the bonding, the membrane 3018 and non-conductive spacers3306 may be etched to form trenches which may be lined with liner 3408and filled with conductive material to form vias 3406. The upper surfaceof the structure may be planarized as appropriate and layers 3410 and3412 may be deposited and patterned to arrive at the device 3400.

Transducer Example 6

FIG. 35 illustrates a further example of an ultrasonic transducerintegrated with a CMOS substrate and formed above a top metal layer ofthe CMOS substrate. The device 3500 includes ultrasonic transducer 3502integrated with CMOS substrate 3504. Device 3500 includes electricalaccess to the topside of membrane 3018. Namely, contacts 3506 areprovided on the topside of the membrane 3018. The contacts may include ametal (e.g., aluminum) or other conductive material, and may includebottom and top liners 3508 a and 3508 b, respectively. In someembodiments, the liners 3508 a and 3508 b may be the same as liners 3013a and 3013 b.

The contacts 3506 may be passivated with layers 3510 and 3512. Layer3510 may be the same material as previously described layer 3410 but maybe thicker. Layer 3512 may be the same material as previously describedlayer 3412 but may be thicker. Layers 3510 and 3512 may be patterned asshown to form a piston membrane configuration in combination withmembrane 3018.

An example of a process for fabricating the device 3500 is nowdescribed. A transfer wafer including the membrane 3018 may be alignedwith and bonded to the substrate 3504. Then the transfer wafer may bethinned as desired (e.g., to remove any bulk substrate and buried oxidelayer) and the contacts 3506 formed. Layers 3510 and 3512 may then bedeposited and patterned in the manner previously described in connectionwith layers 3410 and 3412 to arrive at the device 3500.

It should be appreciated from the foregoing discussion of examples ofultrasonic transducers integrated with CMOS substrates that theprocesses used to fabricate such devices may be low temperatureprocesses. The temperatures of all steps performed involving the CMOSsubstrate once circuit structures are formed on the substrate, includingwafer bonding to a transfer wafer, anneals, or other steps, may be keptbelow temperatures which would cause damage to such circuit components.

Various examples of ultrasonic transducers integrated with a CMOSsubstrate have been described. It should be appreciated that suchdevices may have any suitable dimensions. Non-limiting examples ofsuitable dimensions have been described at least in connection with FIG.30A, for example for the dimensions of the cavity of the ultrasonictransducer and the thickness of the membrane overlying the cavity. Suchdimensions may apply to any of the examples of ultrasonic transducersdescribed herein.

Transfer Wafers

Various examples of transfer wafers have been described herein for usewith various embodiments. In some embodiments, traditional SOI wafersmay be used, having a silicon bulk wafer as a handle layer, buried oxidelayer, and monocrystalline silicon layer. However, as previouslydescribed, some embodiments implement alternative types of transferwafers, including transfer wafers having polysilicon or amorphoussilicon layers, for example when such materials are to be used as themembrane 3018. Applicants have appreciated that transfer wafers havingsuch materials may be implemented in some embodiments instead oftraditional SOI wafers, and that such alternative types of transferwafers may be fabricated with significantly less effort and cost thanrequired to form traditional SOI wafers.

Wafers Including Multiple Ultrasonic Transducers

The examples of FIGS. 30A, 31A, 32A, 33, 34, and 35 illustrate a singleultrasonic transducer integrated with a CMOS substrate. It should beappreciated, however, that the ultrasound transducer probes describedherein may include more, and in some cases many more, ultrasonictransducers integrated with a CMOS substrate. For example, a singlesubstrate (e.g., a single CMOS wafer) may have tens, hundreds,thousands, tens of thousands, hundreds of thousands, or millions of CUTsformed therein. Formation of such large numbers of ultrasonictransducers on a single substrate may be facilitated by use of thewafer-level processes described herein.

When multiple ultrasonic transducers are formed on a CMOS substrate,they may optionally be electrically interconnected in various manners toform a desired device. For example, multiple ultrasonic transducers maybe electrically tied by way of the top metal layer 3014 previouslydescribed. Other manners of providing electrical interconnection arealso possible.

Forms of Integration of Ultrasonic Transducers with Substrates andCircuitry

While various aspects and embodiments have been described as providingmonolithically integrated ultrasonic transducers and CMOS wafers havingICs formed therein, not all aspects and embodiments are limited in thisrespect. For example, some aspects of the present application may alsoapply to flip-chip bonded and multi-chip configurations. For example,making electrical contact to the bottom side of a membrane may beperformed in flip-chip bonded configurations. Other aspects may alsoapply to non-monolithic devices.

As described previously, an aspect of the present application providesan ultrasonic transducer cell integrated with CMOS circuitry where thecircuitry is disposed beneath the transducer. FIG. 36 illustrates anon-limiting example of a such a device, using the ultrasonic transducerof FIG. 30A.

As shown, the device 3600 may include the ultrasonic transducer of FIG.30A with the addition of an integrated circuit 3602. The integratedcircuit may be formed in the substrate 3006 of the CMOS wafer. Forexample, the substrate may be a bulk silicon wafer, and the integratedcircuit 3602 may include one or more active silicon circuit elements(e.g., MOS transistors having doped source and drain regions in thesilicon), capacitors, resistors, or other circuit components. Theintegrated circuit 3602 may be suitable to operate the ultrasonictransducer in transmit and/or receive modes.

As shown, both the electrode 3022 and the conductive contacts 3028 a and3028 b may be connected to the integrated circuit 3602, for example byrespective vias. For instance, the electrode 3022 may be connected tothe integrated circuit 3602 by vias 3007. 3009, and 3026 b. Theconductive contact 3028 b may be connected to the integrated circuit3602 by vias 3604, 3606, and 3026 c. The via connecting the electrode3022 may, for example, directly contact a doped source/drain terminal ofa MOS transistor in the substrate 3006.

As shown in FIG. 36, in some embodiments local connection may be made tothe membrane of an ultrasonic transducer rather than global connection.For example, conductive contacts 3028 a and 3028 b provide for localconnection to the membrane 3018 of the illustrated ultrasonictransducer.

In some embodiments, the membrane of the ultrasonic transducer may bebiased. In such situations, the membrane may be connected to theintegrated circuit 3602 via a capacitor (not shown) for providing ormaintaining a desired bias level. Other biasing configurations are alsopossible.

In some embodiments, the electrode 3022 may be driven, and thus theintegrated circuit 3602 may be suitably connected to drive the electrode3022. In some embodiments, the electrode 3022 may be biased, rather thanthe membrane.

Transducer Fabrication Technology

The various non-limiting examples of ultrasonic transducers fabricatedon CMOS substrates described herein may be fabricated with any suitablefeature sizes. According to an embodiment, 0.18 micron technology may beutilized for fabricating such ultrasonic transducers. In someembodiments, 0.13 micron technology may be used. In some embodiments, 90nm fabrication technology may be used. In some embodiments, 0.35 microntechnology may be utilized. Other feature sizes may be used, as thoselisted represent non-limiting examples.

Various non-limiting examples of ultrasonic transducers which may beused in an ultrasound transducer probe according to one or more aspectsof the present application have been described. It should beappreciated, however, that not all aspects of the present applicationare limited to using such ultrasonic transducers.

The illustrated examples of devices 3000, 3100, 3200, 3300, 3400, and3500 have been described primarily as utilizing aluminum metalprocessing techniques. However, other techniques of forming ultrasonictransducers integrated with CMOS substrates may alternatively be used.For example, copper processing techniques, such as damascene or dualdamascene processing may be used in some embodiments. For suchprocessing, the interlayer dielectrics used may include SiO₂ or otherlow-K materials, where K represents the dielectric constant. Barrierlayers used in combination with copper metallization may includetantalum (Ta), tantalum nitride (TaN), and TiN. Thus, according toaspects of the present application an integrated device may include oneor more ultrasonic transducers integrated with a CMOS substrateincluding CMOS integrated circuitry having copper metallization, andformed using damascene or dual damascene processing.

In some embodiments, a combination of aluminum processing and copperprocessing techniques may be implemented. For example, referring to thedevice 3000, the underlying CMOS substrate may be formed usingcopper-based dual damascene processes. The top metal layer 3014 may bealuminum or aluminum-copper. Thus, a combination of copper processingtechniques and aluminum processing techniques may be utilized tofabricate such devices.

Process

As described previously, aspects of the present application provide anultrasound transducer probe which may be tiled and interconnected bysuitably replicating the ultrasound transducer probe. According to someaspects, such replication may be performed using a commonphotolithography mask or reticle with appropriate stepping and/orscanning functions. Various examples are now described.

According to an aspect of the present application, an ultrasoundtransducer probe may be fabricated by suitably rotating and printing apattern from a photolithography mask (also referred to herein as a“pattern mask”) to create two side-by-side (or horizontally tiled)instances of the pattern. Referring to FIG. 38, a reticle 3800 may havea pattern formed thereon. The pattern may include features at leastpartially defining processing circuitry of an ultrasound transducerprobe and ultrasonic transducers of the ultrasound transducer probe. Asan example, the features may at least partially define I/O circuitry ona side or periphery of the ultrasound transducer probe, for exampleconsistent with the configuration of previously described ultrasoundtransducer probe 200 of FIG. 2A. More specifically, the reticle 3800 maybe a reticle used to fabricate the ultrasound transducer probe 200 in anon-limiting embodiment. The features 3802 may at least partially defineI/O circuitry of the ultrasound transducer probe. The pattern on thereticle may also include an alignment mark 3804.

An ultrasound transducer probe of the type 220 illustrated in FIG. 2Cmay be fabricated by printing the pattern from the reticle 3800 twice.For example, the pattern from the reticle may be printed on a wafer afirst time (by illuminating the reticle), indicated as R0. The wafer maythen be rotated and aligned with the already-printed pattern, and thepattern from the reticle 3800 may again be printed on the wafer (byagain illuminating the reticle), indicated as R180. Alternatively, thereticle may be rotated (rather than the wafer), or both the reticle andwafer may be rotated. In some embodiments, printing the reticle patternat the position of R0 may involve printing the odd fields of the patternand printing the reticle pattern at the position R180 may involveprinting the even fields of the pattern. However, alternative manners ofoperation are possible. By suitably rotating and printing the reticlepattern, as described, a double-wide ultrasound transducer probe (e.g.,ultrasound transducer probe 220) may be fabricated from a singlereticle.

Another manner of horizontally tiling ultrasound transducer probes ofthe types described herein involves printing portions of a reticle inalignment with each other, and is described in connection with FIGS.39-41. FIG. 39 illustrates a reticle 3900 having features at leastpartially defining I/O circuitry 3902 a and 3902 b on opposite sides ofthe reticle. The reticle pattern may also include features betweenpositions B and C for defining, at least in part, ultrasonic transducersof an ultrasound transducer probe. In some embodiments, the reticlepattern may be substantially uniform over the distance WS in the widthdirection. It should be appreciated that the reticle 3900 may besuitable for use in fabricating an ultrasound transducer probe of thetype 210 of FIG. 2B.

The reticle 3900 may be considered to have multiple portions defined bythe positions A-D. For example, position A to B represents a portion,position A to C another portion, position B to C another portion,position B to D another portion, and so on for all combinations ofpositions A-D. Printing appropriate portions and aligning them mayresult in creation of an ultrasound transducer probe. Alignment marksmay be provided at the positions A-D to facilitate printing of theportions and aligning them.

The double-wide ultrasound transducer probe 4000 of FIG. 40 may beprinted by printing and aligning portions of the pattern of reticle 3900of FIG. 39. In one photolithography printing step, a first portion ofthe pattern of reticle 3900 may be printed from position A to position C(see FIG. 39) by scanning the reticle 3900 from position A to positionC. The result is shown as pattern 4002 in FIG. 40. When scanning thereticle 3900 from position A to position C, the features to the right ofposition C in FIG. 39 may be obstructed, for example using bladingtechniques.

Next, the reticle 3900 may be stepped such that position B on thereticle aligns with position C on the printed pattern. A second portionof the reticle 3900 may then be scanned from position B to position D.The result is shown as pattern 4004 in FIG. 40.

Thus, it should be appreciated that the ultrasound transducer probe 4000may include I/O circuitry on opposing ends and a central regioncomprising ultrasonic transducers. Also, such horizontal tiling may beachieved with a single photolithographic mask, thus greatly simplifyingthe process and cost compared to if multiple masks were used.

FIG. 41 illustrates an ultrasound transducer probe 4100 which may beformed by horizontally tiling three instances of the reticle patternfrom reticle 3900 of FIG. 39. At a first stage of processing, a firstportion of the reticle 3900 may be scanned from position A to positionC. The result is shown as 4102. Subsequently, the reticle may be steppedsuch that position B on the reticle aligns with position C on theprinted pattern. A second portion of the reticle 3900 may then bescanned from position B to position C. The result is shown as 4104. Thereticle 3900 may then be stepped again such that position B on thereticle aligns with position C on the printed pattern 4104. A thirdportion of the reticle may then be scanned from position B to positionD. The result is shown as 4106. In this manner, a three-wide ultrasoundtransducer probe may be formed from a single reticle. It should beappreciated that additional instances of the ultrasound transducer probelayout corresponding to reticle 3900 may be horizontally tiled byutilizing a similar methodology and adding in additional scans fromposition B to position C.

When scanning only a portion of a reticle (e.g., from position A toposition C of reticle 3900, from position B to position C of reticle3900, and from position B to position D of reticle 3900), bladingtechniques or other suitable techniques may be used to obstruct orotherwise avoid printing undesired portions of the reticle pattern.

It should be appreciated from the foregoing that multiple instances ofan ultrasound transducer probe may be horizontally tiled on a wafer toform an ultrasound transducer probe of desired dimensions using a commonreticle. Vertical tiling may be accomplished by stepping the reticlevertically and suitably aligning it. Thus, multiple instances of anultrasound transducer probe may be tiled horizontally and/or vertically.

Moreover, it should be appreciated that blading techniques may be usedto facilitate tiling of ultrasound transducer probes having peripheralregions on the top and/or bottom side of the transducer probe whilestill providing a contiguous region of ultrasonic transducers. Forexample, peripheral regions of an ultrasound transducer probe located onthe top and bottom sides of the transducer probe and having only contactpads may be vertically tiled while still creating a contiguous region ofultrasonic transducers by blading one or more of such peripheralregions.

CONCLUSION

The aspects of the present application may provide one or more benefits,some of which have been previously described. Now described are somenon-limiting examples of such benefits. It should be appreciated thatnot all aspects and embodiments necessarily provide all of the benefitsnow described. Further, it should be appreciated that aspects of thepresent application may provide additional benefits to those nowdescribed.

Some aspects of the present application provide ultrasound transducerprobes which are configured to be tiled and interconnected, thusproviding an ultrasound probe designer great flexibility in designing anultrasound probe of choice by mere replication and suitable placement ofa common building block ultrasound unit. Some aspects provide ultrasoundtransducer probes which are connectable to different types of externaldevices via different physical interfaces, thus increasing usability andaccessibility of the devices. Some aspects provide an ultrasoundtransducer probe that is configurable to operate in various modes,including various ultrasound imaging modes. In some aspects, theultrasound transducer probes may be highly integrated, includingultrasound transducers and ICs monolithically integrated on a commonsubstrate, providing a compact form factor.

Ultrasound transducer probes according to aspects of the presentapplication may be worn, and used in-situ. Thus, the usefulness of suchdevices may be greater than conventional ultrasound probes.

Having thus described several aspects and embodiments of the technologyof this application, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those of ordinaryskill in the art. Such alterations, modifications, and improvements areintended to be within the spirit and scope of the technology describedin the application. For example, those of ordinary skill in the art willreadily envision a variety of other means and/or structures forperforming the function and/or obtaining the results and/or one or moreof the advantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the embodimentsdescribed herein. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific embodiments described herein. It is, therefore, to beunderstood that the foregoing embodiments are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, inventive embodiments may be practiced otherwisethan as specifically described. In addition, any combination of two ormore features, systems, articles, materials, kits, and/or methodsdescribed herein, if such features, systems, articles, materials, kits,and/or methods are not mutually inconsistent, is included within thescope of the present disclosure.

The above-described embodiments can be implemented in any of numerousways. One or more aspects and embodiments of the present applicationinvolving the performance of processes or methods may utilize programinstructions executable by a device (e.g., a computer, a processor, orother device) to perform, or control performance of, the processes ormethods. In this respect, various inventive concepts may be embodied asa computer readable storage medium (or multiple computer readablestorage media) (e.g., a computer memory, one or more floppy discs,compact discs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other tangible computer storage medium) encoded with one ormore programs that, when executed on one or more computers or otherprocessors, perform methods that implement one or more of the variousembodiments described above. The computer readable medium or media canbe transportable, such that the program or programs stored thereon canbe loaded onto one or more different computers or other processors toimplement various ones of the aspects described above. In someembodiments, computer readable media may be non-transitory media.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects as described above. Additionally,it should be appreciated that according to one aspect, one or morecomputer programs that when executed perform methods of the presentapplication need not reside on a single computer or processor, but maybe distributed in a modular fashion among a number of differentcomputers or processors to implement various aspects of the presentapplication.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

When implemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer, as non-limitingexamples. Additionally, a computer may be embedded in a device notgenerally regarded as a computer but with suitable processingcapabilities, including a Personal Digital Assistant (PDA), a smartphone or any other suitable portable or fixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audibleformats.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks or wired networks.

Also, as described, some aspects may be embodied as one or more methods.The acts performed as part of the method may be ordered in any suitableway. Accordingly, embodiments may be constructed in which acts areperformed in an order different than illustrated, which may includeperforming some acts simultaneously, even though shown as sequentialacts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Elements other than those specificallyidentified by the “and/or” clause may optionally be present, whetherrelated or unrelated to those elements specifically identified. Thus, asa non-limiting example, a reference to “A and/or B”, when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A only (optionally including elements other than B);in another embodiment, to B only (optionally including elements otherthan A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

As used herein, the term “between” is to be inclusive unless indicatedotherwise. For example, “between A and B” includes A and B unlessindicated otherwise.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively.

What is claimed is:
 1. An apparatus, comprising: a semiconductor chipincluding a silicon substrate, a plurality of insulating layers formedon the silicon substrate, and a metal layer between two insulatinglayers of the plurality of insulating layers, wherein the metal layer isconnected to the silicon substrate by a conductive via passing throughan insulating layer of the plurality of insulating layers, thesemiconductor chip having a device surface with a width and height, thewidth of the device surface being at least twice as large as the heightof the device surface, the metal layer having a thickness between 0.5microns and 10 microns, wherein the width, the height, and the thicknessare orthogonal to each other; a plurality of complementary metal oxidesemiconductor (CMOS) ultrasonic transducers integrated on the pluralityof insulating layers, wherein at least one CMOS ultrasonic transducer ofthe plurality of CMOS ultrasonic transducers is disposed above the metallayer such that the metal layer is between the silicon substrate and theat least one CMOS ultrasonic transducer; and CMOS control circuitryformed in the silicon substrate, coupled to the plurality of CMOSultrasonic transducers by at least one conductive via passing throughthe insulating layer of the plurality of insulating layers andconfigured to control the plurality of CMOS ultrasonic transducers tosupport one-dimensional (1D), two-dimensional (2D), andthree-dimensional (3D) ultrasound imaging, wherein the CMOS controlcircuitry comprises a waveform generator coupled to the at least oneCMOS ultrasonic transducer of the plurality of CMOS ultrasonictransducers through a pulser, the waveform generator configurable togenerate an impulse, a continuous wave, a coded excitation, and a chirpwaveform; wherein the waveform generator comprises a plurality ofregisters, wherein the plurality of registers comprises a registerstoring a value of an initial phase, a register storing a value of aninitial frequency, and a register storing a value of a frequency rate ofchange; and wherein the waveform generator further comprises a pluralityof comparators and a plurality of multiplexers, wherein outputs of theplurality of registers are coupled to inputs to the plurality ofcomparators, and wherein outputs of the plurality of comparators arecoupled to inputs of the multiplexers, an output of a first multiplexerof the plurality of multiplexers being a first input to the pulser, andan output of a second multiplexer of the plurality of multiplexers beinga second input to the pulser.
 2. The apparatus of claim 1, wherein theplurality of CMOS ultrasonic transducers and the CMOS control circuitryrepresent multiple instances of an ultrasound probe tiled on the siliconsubstrate.
 3. The apparatus of claim 1, wherein the CMOS controlcircuitry is configured to control the at least one CMOS ultrasonictransducers of the plurality of CMOS ultrasonic transducers to providehigh intensity focused ultrasound (HIFU).
 4. The apparatus of claim 1,wherein the plurality of CMOS ultrasonic transducers is a firstplurality of CMOS ultrasonic transducers, and wherein the apparatusfurther comprises a second plurality of CMOS ultrasonic transducersconfigured to provide high intensity focused ultrasound (HIFU).
 5. Theapparatus of claim 1, wherein the pulser is a tri-level pulser.
 6. Theapparatus of claim 1, wherein the pulser is configured to providevoltage pulses to the at least one CMOS ultrasonic transducer of theplurality of CMOS ultrasonic transducer having voltages between 30 Voltsand 120 Volts.
 7. The apparatus of claim 1, wherein the chirp waveformis a linear frequency modulation (LFM) chirp.
 8. The apparatus of claim1, wherein a ratio of the width of the device surface to the height ofthe device surface is between 5:1 and 10:1.
 9. The apparatus of claim 1,wherein the plurality of CMOS ultrasonic transducers covers more thanhalf of the height of the device surface and less than the width of thedevice surface, and wherein at least a first portion of the CMOS controlcircuitry is formed on a peripheral region of the width of the devicesurface not covered by the plurality of CMOS ultrasonic transducers. 10.The apparatus of claim 1, wherein the at least one CMOS ultrasonictransducer of the plurality of CMOS transducers comprises a membrane,and wherein the membrane is connected to the metal layer by anelectrically conductive via.
 11. The apparatus of claim 1, furthercomprising a wiring line in the silicon substrate, wherein the at leastone CMOS ultrasonic transducer of the plurality of CMOS ultrasonictransducers comprises an electrode, and wherein the metal layer isconfigured as an electrical shield between the electrode and the wiringline.
 12. The apparatus of claim 1, wherein the CMOS control circuitryincludes a sequence processor configured to store a program controllinga sequence of operations executed by the plurality of CMOS ultrasonictransducers.
 13. The apparatus of claim 1, wherein the CMOS controlcircuitry comprises a sequence processor configured to operate theplurality of CMOS ultrasonic transducers semi-autonomously.
 14. Theapparatus of claim 1, wherein the plurality of CMOS ultrasonictransducers are arranged in groups connected in a daisy-chainconfiguration by data lines.
 15. The apparatus of claim 1, furthercomprising time-gain compensation circuitry coupled to the plurality ofCMOS ultrasonic transducers.